CHEM 237...

does b.p. and m.p. increase or decrease with increasing molar mass in alkanes?

increase because dispersion forces increase as the molecule increases.

alkane branching affect on b.p.

increased branching lowers b.p. because less surface area for contact between neighboring molecules (i.e. less dispersion forces)

angle puckering in cyclobutane

increases angle strain, but decreases torsional strain

radical

substance that contains a single, unpaired valence e⁻ (e.g. pentadienyl C₅H₇)

intermediate carbocation

not stable in aqueous environment and is quickly attacked by water molecule from both sides since it is planar

The first step in the reaction mechanism of oxidation of secondary alcohols with sodium hypochlorite is?

replacement of the alcohol proton with Cl+

steric strain

repulsive interaction that occurs when atoms are forced closer together than their atomic radii allow (i.e. H within the Van der Waals radius) -between bonding and anti bonding orbitals in close proximity

What is the equation relating volume and mole fraction?

volume1 = (mole fraction1 x molar mass1)/(density1)

What ion did the benzyltri-n-butylammonium cation transport from the aqueous to organic phase in the phase-transfer catalysis experiment? a. sodium cation b. chloride anion c. bromide anion d. allyl bromide e. naphtholate anion

e

What is the hybridization of the oxygen atom and the approximate bond angles around oxygen in methanol, CH3OH? a. sp and 120° d. sp3 and 120° b. sp and 180° e. sp3 and 109.5° c. sp2 and 109.5°

e

electrostatic potential maps

show calculated charge distributions -e⁻ rich: red -e⁻ poor: blue

Woehler (1828)

showed that it was possible to convert an inorganic salt called ammonium cyanate into an organic substance called urea

Acetone is flammable

True

After a ring flip, an axial substituent in one chair form becomes an equatorial substituent.

True

Concentrated acetic acid is corrosive.

True

Each carbon in cyclohexane is bonded to one axial and one equatorial hydrogen.

True

Ethyl Acetate is flammable

True

Hexane is flammable

True

Hypochlorous acid is an oxidizing agent.

True

If one is going to re-extract the upper layer with another volume of liquid, the upper layer can be left in the separatory funnel and fresh solvent added to the funnel.

True

Methylene chloride is a probable human carcinogen.

True

Only touch the edges of the plate. (T/F)

True

Recrystallization is the process of dissolving a solid material into a suitable solvent or mixture of solvents and allowing the material to crystallize from this solution. (T/F)

True

Recrystallization requires the material that is to be purified is a solid. (T/F)

True

Rf is dependent on polarity. (T/F)

True

Rf values should be kept in the range of 0.2 to 0.8 for the most effective separation when more than one compound is present in the sample. (T/F)

True

Sodium hydroxide can cause severe damage to skin and eyes.

True

Spot the plate on the dull, not shiny side of the plate. (T/F)

True

Spots should be 1 to 2 mm in diameter. (T/F)

True

Substituents larger than hydrogen prefer to adopt equatorial positions due largely to a smaller amount of steric strain.

True

The Rf value is defined as the ratio between the distance the spot moved and the distance the solvent moved. (T/F)

True

The different geometries that a molecule can attain by bond rotations and bends are called conformations.

True

The distance the solvent moved is where the spot started to where the solvent front ended up. (T/F)

True

The distance the spot moved is where the spot started to the center of where it ended up. (T/F)

True

The first step in using a separatory funnel for extraction is to make sure the funnel stopcock is closed and then carefully pour the liquid to be extracted into the funnel.

True

The stopcock can be used to vent excess pressure if either of the liquids are warm to the touch and has a low boiling point.

True

Use clamps to secure the filter flask to avoid tipping and unnecessary exposure to hot liquids or the solute. (T/F)

True

difference between constitutional isomers and conformational isomers

conformational isomers cannot be isolated because they change between structures too rapidly

acid strength: hybridization

conjugate bases increase stability from sp³→sp. electron density is pulled into the molecule

During a solvent extraction between water and an immiscible solvent, a student has two layers in their separatory funnel and then shakes it. A single, milky liquid develops and no real sign of any layers are visible. What has occurred and what should the student do?

-an emulsion has formed. -First, add a small quantity of water. If that does not work, then add solvent.

cis-trans isomerism in cycloalkanes

-less flexible than open chain alkanes, which means less conformational freedom -have "top" face and "bottom" face when viewed on edge -possible in substituted cycloalkanes

sp hybridization

2s orbital combines with only one of the three p orbitals (two 2p orbital for π bonding) linear and 180°

sp² hybridization

2s orbital combines with only two of the three p orbitals (one 2p orbital for π bonding). double bond is less than twice as strong as single bond because the sideways overlap in π is not as great as head-on overlap in σ bonding. planar and 120°

sp³ hybridization

2s orbital combines with three 2p orbitals. intermediate in energy because one of the lobes is larger and can overlap more effectively (form stronger bonds) tetrahedral and 109.5°

For hot vacuum filtration, the filter paper should be completely dry when pouring the hot solution into the Buchner funnel to filter. (T/F)

False

Gloves and goggles are not required when handling sodium hydroxide.

False

Hold your thumb firmly over the hole in the top of the funnel during shaking.

False

It is acceptable to handle TLC plates with bare hands.

False

Lachrymators like allyl bromide are specifically dangerous because of their explosion hazard.

False

Mark the plate after applying the sample. (T/F)

False

Methylene chloride is flammable.

False

Pipets that contain only water can be disposed of in the trash.

False

Polar compounds will have higher Rf values than nonpolar compounds under the same developing conditions. (T/F)

False

Rf is not dependent on polarity. (T/F)

False

Silica is toxic

False

Students should throw away the first layer and acid washes.

False

The less polar the solvent, the higher the Rf values. (T/F)

False

The primary risk associated with dichloromethane is its flammability.

False

The twist boat conformation of cyclohexane has angle strain but is almost free of steric strain.

False

Unused allyl bromide can be disposed of in the aqueous waste.

False

Use a pencil or pen to mark the position of a spot on the TLC plate. (T/F)

False

Eugenol will give a positive result for which tests?

Ferric chloride, Bromine, and Permanganate

alkane nomenclature: 13 C

tridecane

Recrystallization is the process of dissolving a solid material into a suitable solvent or mixture of solvents and allowing the material to crystallize from this solution.

true

Recrystallization requires the material that is to be purified is a solid.

true

Use clamps to secure the filter flask to avoid tipping and unnecessary exposure to hot liquids or the solute.

true

quantum mechanics

uses mathematical equations to describe the motion of an e⁻ around a nucleus

what does molecular polarity result from?

vector summation of individual bond polarities and lone-pair contributions

Is water or chloride ion stronger as a base?

water

what are we eliminating

water

what did we wash distillate with

water and NaCl

A student was given a sample of crude acetanilide to recrystallize. The initial mass of the the crude acetanilide was 146 mg. The mass after recrystallization was 125 mg. Calculate the percent recovery from recrystallization.

85.62%

Compared to the dichromate oxidizing agents, hypochlorous acid (prepared from household bleach) is ...

-safe -environmentally sound -inexpensive

ratio of cyclohexanes in twist boat to chair forms

1 in every 10,000

(Recrystallization of Acetanilide) The proper solvent choice is crucial for effective recrystallization. What are the features of a good recrystallization solvent? Select all that apply. a. The crude compound should be soluble in this solvent at room temperature. b. The solvent should have a high boiling point. c. We should be able to easily remove the solvent from the purified product. d. The solvent should not react with the target substance. e. The solvent should dissolve a moderate quantity of the target substance near its boiling point but only a small quantity near 0 °C.

cde

organic acids

characterized by the presence of a positively charged polarized hydrogen atom (blue in electrostatic potential maps)

organic bases

characterized by the presence of an atom with a lone pair of electrons that can bond to H⁺

formal charge

charge an atom would have if all the bonding e⁻ were shared equally between bonded atoms (e⁻ "bookkeeping") -always want less formal charge and negatives should go on the more EN atoms

The solubility of acetanilide is 3.53 g in 100 mL of chloroform at 0 °C, and 29.1 g in 100 mL of chloroform at 60 °C. What is the maximum percent recovery that can be achieved for the recrystallization of acetanilide from chloroform?

87.87%

percent of the 50 million known chemicals that contain carbon?

90%

(Recrystallization of Acetanilide) The solubility of acetanilide is 0.53 g in 100 mL of ice-cold water, and 5.5 g in 100 mL of boiling water. What is the maximum percent recovery that can be achieved for the recrystallization of acetanilide from water?

90.4%

A student's kinetic study of the SN1 solvolysis reaction of 1‐phenyl‐1‐chloroethane (using dilute NaOH to neutralize the HCl formed) gave a rate constant k=5.0 x 10‐4sec‐1, using a 70% H2O, 30% ethanol mixture for solvent. What effect would doubling the base concentration have on the rate constant? a. the rate would double b. the rate would increase by a factor of 4 c. it would stop the reaction completely d. the rate would be unchanged e. the rate would be decreased by a factor of 2

d

Absorption of infrared radiation by a molecule a. causes excitation of the outer electrons b. causes changes in the nuclear spin c. produces a triplet state d. produces changes in the amplitude of molecular vibrations e. breaks the molecule into fragments

d

The technique of simple distillation: a. can be used as a means of separation b. can be used as a means of purification c. is based upon differences in boiling points of two substances d. a and b e. a, b and c

e

(Recrystallization of Acetanilide) A student was given a sample of crude acetanilide to recrystallize. The initial mass of the the crude acetanilide was 131 mg. The mass after recrystallization was 121 mg. Calculate the percent recovery from recrystallization.

92.4%

During a melting point determination, it is normal to first take a rapid rough measurement followed by a slower more accurate measurement. Why is it important to allow the Mel-Temp to cool 15 °C before placing the second capillary tube in, and to set the voltage generate 1-2 °C temperature increase per minute?

A rapid temperature increase will give a melting point range that is too high.

During a melting point determination, it is normal to first take a rapid rough measurement followed by a slower more accurate measurement. Why is it important to allow the Mel-Temp to cool 15°C before placing the second capillary tube in, and to set the voltage generate 1°-2°C temperature increase per minute?

A rapid temperature increase will give a melting point range that is too high.

The active ingredients in an over the counter analgesic pill were separated by TLC on silica, using a solvent system of hexane and ethyl acetate. Identify where the waste generated by this process should go. Drag and drop the chemical wastes generated in this reaction into the appropriate container.

Hexane, ethyl acetate, and acetone should go in the non-halogenated organic waste container. TLC plates and spotting capillaries should go to the solid waste container.

To get effective mixing in a separatory funnel, the combined level of liquids should not exceed: The lower part of the neck of the separatory funnel. Higher than the stopcock. Higher than the widest part of the separatory funnel. More than half of the separatory funnel.

Higher than the widest part of the separatory funnel.

Purpose? Allyl bromide was used in excess.

Keep the time for the reaction to go to completion under an hour.

correct reading of a buret

at meniscus with one definite decimal and one estimate decimal

A compound to be recrystallized should be: a. soluble in any solvent b. soluble in organic solvent only c. soluble in water only d. slightly soluble at low temperature and highly soluble at high temperature e. slightly soluble at high temperature and highly soluble at low temperature

d

A student is comparing two samples of crystalline organic solids. A TLC analysis shows a single spot for each sample and the co-spot with the same Rf value. Which of the following would provide the most conclusive evidence that the two samples are the same compound?

Perform a mixture melting point.

why does 1-phenyl-1-chloroethane undergo solyvolysis in polar solvents

because it is a secondary benzylic halide and the corresponding carbocation is stabilized by resonance with the aromatic ring

What is the relationship between substitution and carbocation stability?

The more substituted a carbocation, the more stable it is.

Which of the following statements about melting point determination is not true?

The presence of impurities introduces entropy, which raises the energy required to melt the substance. (The melting range for pure materials, measured from the first observed sign of melting to the last observed sign of remaining solid, is typically less than 2 °C. Impurities increase the entropy and reduce the energy required to cause melting. Literature values are often just the upper limit of the melting range.)

what does every covalent bond have?

a characteristic bond strength and bond length

What product(s) can be prepared through the oxidation of primary alcohols?

aldehydes and carboxylic acids

the reaction rate is equal to the rate of disappearance of RCl

and the appearance of HCl

Cyclohexanol is oxidized by a mixture of sodium hypochlorite and acetic acid. The solution is treated with sodium bisulfite and sodium hydroxide, before the product is extracted into dichloromethane. The organic layer was dried over potassium carbonate, decanted, and the product was obtained when the solvent was evaporated.

aqueous waste/sink: aqueoous layer after extraction solid waste: potassium carbonate, potassium iodide/starch strip chlorinated organic waste: dichloromethane non-chlorinated organic waste: cyclohexanone product

functional group: sulfide

R-S-R (sulfide)

functional group: alkyl halide

R-X (none)

A student was given a sample of crude acetanilide to recrystallize. The initial mass of the the crude acetanilide was 131 mg. The mass after recrystallization was 125 mg. Calculate the percent recovery from recrystallization.

% recovery = mass after recrystallization/initial mass * 100% 125/131*100 = 95.4%

properties of alkanes

(aka paraffins) -low affinity for other compounds because they are fairly unreactive -not often involved in the chemistry of living organisms -combustable: react with O₂ to burn under certain conditions -halogenation: react with Cl₂ in the presence of light to replace H's with Cl's. CH₄ + Cl → CH₃Cl + HCl (hard to control because CH₃Cl can keep reacting with Cl₂)

At the end of an experiment, a student has an unused portion of reagent. Where should he or she place it?

- See if anyone else doing the experiment needs some of the reagent. - In the properly marked waste conainer

acid-base reaction prediction

-H⁺ will always go from the stronger acid to the stronger base (lower pKa has priority) -product conjugate acid must be weaker and less reactive than the starting acid

Which of the following statements describe why moisture must be excluded from any sample injected into the G.C. Select all answers that apply.

-Water is very slow to elute from the column. -Water contains dissolved salts that can degrade the column.

Which of the following are appropriate attire for the chemistry laboratory?

-enclose safety goggles -nitrile resistant gloves

In which of the following ways is the use of an infrared spectrophotometer fitted with an ATR sample advantageous over a beam-through-sample spectrophotometer? Select all answers that apply. -beam-through-sample techniques have issues with nonpolar materials -the ATR crystal is not degraded by the presence of water -the same ATR sample holder may be used for liquid samples and solid samples -ATR can be used to analyze toxic materials.

-the ATR crystal is not degraded by the presence of water -the same ATR sample holder may be used for liquid samples and solid samples

For SN1 solvolysis of t-butyl chloride, rank the solvents from fastest reaction to slowest reaction.

-water -formic acid -methaol -ethanol -acetone -acetic acid

what was the alkyl halide reactant

1-phenyl-1-chloroethane

The slow step in the conversion of alcohol to an alkyl halide by an SN1 mechanism is the loss of water from the protonated alcohol to form the carbocation intermediate. Rank the following molecules in terms of their rate of reaction, fastest at the top.

1. 1-methylcyclohexanol 2. cyclohexanol 3. 1-hexanol

three rules for determining ground state electron configurations

1. Aufbau Principle: fill lowest energy orbitals first 2. Pauli Exclusion Principle: max of 2 e⁻ per orbital 3. Hund's Rule: fill degenerate orbitals singly first with parallel signs

Label the following statements concerning TLC as true or false. 1. Use a pencil or pen to mark the position of a spot on the TLC plate. 2. Spot the plate on the dull, not shiny side of the plate. 3. Only touch the edges of the plate. 4. Mark the plate after applying the sample. 5. Spots should be 1 to 2 mm in diameter.

1. F 2. T 3. T 4. F 5. T

(Recrystallization of Acetanilide) Procedure: 1. Place the finely divided mixture and a boiling chip into an Erlenmeyer flask on a steam bath. 2. Add the minimum amount of hot water to dissolve the solid. 3. Rapidly filter the hot solution through a pre-warmed funnel. 4. Wash the filter with hot solvent and transfer the filtrate to a clean flask. 5. Allow the filtrate to cool slowly, then cool in an ice bath to force precipitation. 6. Vacuum filter the cold suspension. 7. Air dry the purified solid on the filter.

1. Place the finely divided mixture and a boiling chip into an Erlenmeyer flask on a steam bath. 2. Add the minimum amount of hot water to dissolve the solid. 3. Rapidly filter the hot solution through a pre-warmed funnel. 4. Wash the filter with hot solvent and transfer the filtrate to a clean flask. 5. Allow the filtrate to cool slowly, then cool in an ice bath to force precipitation. 6. Vacuum filter the cold suspension. 7. Air dry the purified solid on the filter.

Acetanilide was recrystallized from the minimum amount of hot water, and collected by vacuum filtration. Identify where the waste generated by this process should go. 1. filtrate 2. filter paper 3. rinse acetone 4. melting point capillary

1. aqueous waste 2. solid waste 3. non-chlorinated organic waste 4. broken glass

two descriptors for atoms

1. atomic number: # of protons 2. mass number: (# of protons) + (# of neutrons)

naming cycloalkanes

1. name the parent by seeing if cycloalkane or chain has more C. 2. # substituents such that the second one has the lowest number possible 3. # different substituents in alphabetical order

factors influencing acid strength

1. periodic table trends 2. Resonance 3. Inductive Effects 4. Hybridization

steps to recrystallization of acetanilide

1. place impure substance and a boiling chip into an erlenmeyer flask on a heating element 2. add minimum amount of hot water to just dissolve the solid 3. rapidly filter hot solution through a pre-warmed funnel 4. wash filter with hot solvent and transfer filtrate to clean flask 5. cool filtrate in ice bath to force precipitation 6. vacuum filter the cold suspension 7. air dry the purified solid on the filter

List the procedural steps required to separate and collect a two-liquid mixture using preparative gas chromatography.

1.)Collect a vial of unknown mixture. Record its number and letter 2.)Inject the mixture into the numbered prep GC instrument that matches the number on your sample vial 3.)Slip a collection tube over the lower exit port of the prep GC just afte rthe first fraction begins to elute 4.)Remove the collection tube when the first peak is almost finished 5.)Add another collection tube and take a center cut for the next fraction 6.)Transfer the samples to conical sample vials by connecting the vials to the collecting tubes 7.)Centrifuge both vials to collect the sample. Cap the vials

What region of an infrared spectrum is most useful for distinguishing between isomers that contain the same functional group?

1400-400 cm-1

How many hydrogens are removed during the oxidation of 3‐heptanol to 3‐heptanone?

2

what was the dehydrating acid used

2:5 sulfuric acid and phosphoric acid

What does the term CARCINOGEN mean?

A substance or agent capable of causing or producing cancer in mammals.

During Thin Layer Chromatography, what method is typically used to apply the dilute solution of the sample to a TLC plate?

A thin glass spotter or capillary tube.

In the reaction to produce allyl 2-naphthyl ether, 2-naphthol is first reacted with aqueous sodium hydroxide to make sodium 2-naphtholate, which then goes on to react with allyl bromide and benzyltributylammonium chloride phase transfer catalyst, with dichloromethane as a solvent. The boxes in the diagram represent the layers inside the reaction flask part-way to completion. Place the labels in the appropriate box. (If a molecule has significant solubility in both layers, it may be used more than once).

AQUEOUS LAYER: (top) -water -sodium 2-naphtholate -sodium hydroxide -benzyltributylammonium chloride ORGANIC LAYER: (bottom) -dichloromethane -allyl bromide -allyl naphthyl ether -benzyltributylammonium chloride

Cyclohexanol is converted to cyclohexanone by hypochlorous acid. Excess hypochlorous acid is removed by adding sodium bisulfite. The aqueous reaction mixture is then saturated with sodium chloride and placed in a separatory funnel with methylene chloride (dichloromethane). The boxes in the diagram represent the layers of the separatory funnel. Place the labels in the appropriate box.

AQUEOUS LAYER: (top) -water -sodium chloride ORGANIC LAYER: (bottom) -methylene chloride -cyclohexanone

Infrared Spectra are recorded using an ATR detector. What does ATR stand for?

Attenuated Total Reflectance

Infrared Spectra are recorded using an ATR detector? What does ATR stand for?

Attenuated Total Reflectance

Infrared spectra are recorded using an ATR detector. What does ATR stand for?

Attenuated Total Reflectance

The William ether synthesis between 2-napthol and allyl bromide in the presence of strong base and benzyltriphenylammonium chloride as a phase transfer catalyst in dichloromethane solution is know to proceed in reasonable yield. Why will the reaction fail to work if the phase transfer catalyst is switched to ammonium chloride while retaining the same reactants, solvent and base?

Because ammonium chloride is not soluble in dichloromethane solvent.

common name: neopentyl

CºCH₂- (º=quaternary C)

Complete the data table by placing a check mark or an X in each box to indicate whether the molecule in each row of the left-most column would give a positive test with the reagents listed in each column.

Bromine Test This test is positive for carbon-carbon double bonds. There are double bonds in cyclohexene, limonene, and eugenol. Potassium permanganate Test This test is positive for carbon-carbon double bonds. There are double bonds in cyclohexene, limonene, and eugenol. Ferric chloride Test This test is positive for phenols. The eugenol contains a phenol group.

relative bond lengths

C-C→C=C→C≡C C-H→C-H→C-H

condensed structures

C-H and C-C single bonds aren't shown; instead they're understood (e.g. CH₃CH(CH₃)₂)

important bonds in organic chemistry

C-H, C-C, C-O, C-N, and C-Li

Select the statement about equatorial and axial positions in cyclohexane that is correct.

Each carbon in cyclohexane is attached to one axial and one equatorial hydrogen.

most important elements in organic chemistry?

CHiNOPS

common name: tert-butyl

CH₃C-(CH₃)₂

common name: isopropyl

CH₃C-HCH₃

common name: isobutyl

CH₃CH(CH₃)CH₂-

common name: isopentyl

CH₃CH(CH₃)CH₂CH₂-

common name: sec-butyl

CH₃CH₂C-HCH₃

common name: tert-pentyl aka tert-amyl

CH₃CH₂Cº- (º=tertiary C)

1-chloro-1-phenylethane undergoes solvolysis in water by an SN1 mechanism to make 1-phenylethanol. The reaction is followed with bromothymol blue indicator and an aliquot of sodium hydroxide base. Which of the following statements about the reaction are true?

Carbocations are stabilized by protic solvents like water. The first step is the slowest because a bond is being broken. The reaction can be followed because acid is produced as a product. The reaction follows first order kinetics because there is one reactant in the rate determining step.

For a successful TLC experiment, you need to pay attention to the details. From the list of instructions and tips below, select the detail that is NOT important to a TLC experiment.

Closely monitor the temperature of the solvent in the chamber.

In the oxidation reaction with sodium hypochlorite, the oxidant is reduced into _____.

Cl‐

What components of the mixture, from the Williamson ether synthesis between 2-napthol and allyl bromide, will elute from the silica gel mini column?

Dichloromethane and allyl naphthyl ether

What will be in the organic bottom layer in the reaction to produce allyl 2-napthyl ether?

Dichloromethane, allyl bromide, allyl 2-naphthyl ether, benzyltributylammonium chloride

Eugenol, the essential oil found in cloves, is insoluble in water. The alcohol group in eugenol is dramatically more acidic than regular straight-chain alcohols. How could eugenol (shown below) be separated from a mixture of other non-acidic molecules? Dissolve the mixture in dichloromethane, shake with hydrochloric acid, collect the aqueous layer, and rebasify to force precipitation of the eugenol. Dissolve the mixture in dichloromethane, shake with hydrochloric acid, collect the organic layer, and evaporate to dryness to recover the eugenol. Dissolve the mixture in water, shake with dichloromethane, collect the organic layer, and evaporate to dryness to recover the eugenol. Dissolve the mixture in dichloromethane, shake with sodium hydroxide, collect the aqueous layer, and reacidify to force precipitation of the eugenol.

Dissolve the mixture in dichloromethane, shake with sodium hydroxide, collect the aqueous layer, and reacidify to force precipitation of the eugenol.

Eugenol, the essential oil found in cloves, is insoluble in water. The alcohol group in eugenol is dramatically more acidic than regular straight-chain alcohols. How could eugenol be separated from a mixture of other non-acidic molecules?

Dissolve the mixture in dichloromethane, shake with sodium hydroxide, collect the aqueous layer, and reacidify to force precipitation of the eugenol.

acid strength: inductive effects

EN atoms take away electron density from the basic sites. therefore, the strongest acid has the most stable conjugate base

Eugenol is the major component of clove oil. Draw the major product of the reaction of eugenol with one equivalent of bromine under the conditions shown. The expected product is a vicinal dibromide.

Electrophilic Addition

T/F - Lachrymators like allyl bromide are specifically dangerous because of their explosion hazard.

FALSE

T/F - The primary risk associated with dichloromethane is its flammability.

FALSE

TRUE OR FALSE: Gloves and goggles are not required when handling sodium hydroxide.

FALSE

TRUE OR FALSE: Unused allyl bromide can be disposed of in the aqueous waste.

FALSE

formal charge equation

FC = (# of VE) - [(# of LPE) + (1/2)(# of BPE)]

For recrystallization, rapid cooling gives the best crystals. (T/F)

False

Identify the apparatus used in a vacuum filtration by dragging and dropping the labels into the appropriate boxes.

Filter paper is placed in the Buchner funnel to collect all the big particles. The Buchner funnel is held down by a vacuum seal by filter adapter (or Filtervac). The filtrate runs into the filter flask. The clamp, usually attached to a ring stand, holds the entire apparatus if it's securely tightened around the neck of the filter flask.

During a solvent extraction between water and an immiscible solvent, a student has two layers in their separatory funnel and then shakes it. A single, milky liquid develops and no real sign of any layers are visible. What has occurred and what should the student do? A phase change has occured. Pour the mixture into a beaker, reheat, and then try to perform the extraction again. First, add a small quantity of water. If that does not work, then add solvent. An emulsion has formed.

First, add a small quantity of water. If that does not work, then add solvent. An emulsion has formed.

Mixture melting point determination, solubility tests, and thin layer chromatography can be used to assess the purity and identity of a substance. Drag and drop each of the chemical wastes generated in this reaction into the appropriate container.

Glass Waste: used melting point capillaries Solid Waste and Used TLC Plates: contaminated paper towels 10% Aqueous Sodium Bicarbonate Waste: sodium bicarbonate solution Hexanes, Ethyl Acetate, Ethanol, Acetone Waste: TLC solvent

strong acids

HCl, HBr, HI, HNO₃ (nitric acid), HClO₄ (perchloric acid), H₂SO₄ (sulfuric acid); acronym: Strong Hurricanes Can Bring In Some₄ Nasty₃ Clouds₄

Which of the following reagents is are oxidizing agents?

HOCl; H2O2; CrO3; KMnO4

Given a spectrum: -Identify what type of spectra it is: NMR, IR, UV/Vis -What is the type of em radiation associated with these peaks: radio waves, infrared radiation, ultraviolet and visible light -What is measured in this spectroscopic method? absorption wavelength related to an excited electron state; vibrational frequency of a bond; frequency that causes a nucleus to flip its spin

IR infrared radiation Vibrational frequency of a bond

How can a student know how much drying agent to use?

If the drying agent swirls, the student has added enough. If all of the drying agent stays clumped together, the student needs to add a little more drying agent to the sample.

Identify the atoms that participate in 1,3-diaxial interactions in the shown conformation of cis-1,2-dimethylcyclohexane.

In cis-1,2-dimethylcyclohexane, one methyl group is axial and one methyl group is equatorial. The axial methyl group experiences a steric repulsion with two axial hydrogens on the same face. The steric repulsion caused by these two 1,3-diaxial interactions destabilizes the molecule by 2 × 0.9 kcal/mol.

Identify the gauche interactions between methyl groups in the shown conformation of cis-1,2-dimethylcyclohexane.

In cis-1,2-dimethylcyclohexane, the methyl groups are separated by a torsion angle of 60°. The steric repulsion caused by this gauche interaction destabilizes the molecule by 3.8 kJ/mol (0.9 kcal/mol).

Select the Newman projection that corresponds to the following molecule.

In the Newman projection, we look down a C-C bond, with the front carbon represented by the point where the three lines meet and the back carbon represented by the circle. Each line represents a C-X bond, where X is hydrogen or any substituent. In this particular case, involving a six-membered ring (cyclohexane), we are looking down two parallel C-C bonds in the Newman projection, hence the presence of two circles and two locations of three intersecting lines. We must carefully check that each substituent is on the correct carbon atom (relative to the positions of the other substituents) and that the substituent has the proper orientation on that ring carbon atom.

Identify the gauche interactions between methyl groups in the shown conformation of trans-1,2-dimethylcyclohexane. How many gauche interactions are there between methyl substituents in this molecule?

In the diequatorial conformer of trans-1,2-dimethylcyclohexane, the methyl groups are separated by a torsion angle of 60°. This gauche interaction destabilizes the molecule by 3.8 kJ/mol (0.9 kcal/mol).

Which of the following statements about IR is not true?

Infrared spectroscopy can be used ot analyze almost any kind of sample.

Which of the following statements about infrared spectroscopy is not true?

Infrared spectroscopy can be used to analyze almost any kind of sample.

Select the statement which is NOT true about the chair conformation of cyclohexame.

It contains six axial hydrogens that are approximately parallel to the plane of the ring.

Identify the apparatus used in a vacuum filtration by dragging and dropping the labels into the appropriate boxes. (PICTURES ON QUIZ)

Know how to ID: flat filter paper, buchner funnel, filter adapter, clamp, filter flask

difference between Lewis structures and Kekulé structures?

Lewis shows e⁻ as only dots and Kekulé shows bonds as lines

Drag and drop the true statements into the box that apply to thin-layer chromatography.

Methods and Procedures: The solvent level should be below the spots Do not allow the edges of the plate to touch the filter paper Allow the Solvent front to get 5 to 10 mm from the top of the plate When the solvent front has reached the correct height, remove from the chamber and immediately draw a line at the solvent front TLC data is interpreted in terms of Rf values Do not allow the solvent front to get within 1 to 2 mm from the top of the plate

Clean Up Procedures

Melting point capillaries, must be disposed of in a glass waste container. Once a paper product is contaminated it can no longer be disposed of in the trash, and must be placed in the appropriate Solid Waste and Used TLC Plates container. The sodium bicarbonate solution is mostly water, and it should be disposed of in an 10% Aqueous Sodium Bicarbonate waste container. TLC solvent is a mixture of ethyl acetate and hexanes; it should be disposed of in the Hexanes, Ethyl Acetate, Ethanol, and Acetone waste container.

hybridization of N and O

N orbitals hybridize into 4 sp³ orbitals (e.g. methylamine NH₂CH₃)

Complete the data table using calculated molar masses and data about solvent densities.

No, density does not always increase as molar mass increases.

List the seven procedural steps, from start to finish, that are required to perform an accurate melting point determination.

Press the open end of a capillary tube into the solid sample Invert the tube and tap gently to move the solid to the bottom of the capillary Place the tube with sample into the melting point apparatus, and heat at 10 degrees per minute Observe the material through the complete melting process to get a rough estimate of the melting range Turn off and allow to cool by 15 degrees Replace the existing tube with a new sample Heat at 2 degrees per minute through the expected range

The carrier gas in a GC separation is usually an inert gas such as nitrogen, helium, or argon, but can also be hydrogen. What are the pros and cons of using hydrogen as a carrier gas in a GC separation?

Pros: -Cheaper than helium -Can be generated at the GC instead of from gas tanks -Greater difference in mass b/w carrier gas and sample than nitrogen Cons: -Explosion hazard

functional group: amide

R-(C=O)-(N-R)-R (-amide)

functional group: aldehyde

R-(C=O)-H (-al)

functional group: anhydride

R-(C=O)-O-(C=O)-R (-oic anhydride)

The image below shows thin-layer chromatography results for two samples, A and B. Calculate the Rf values for both samples. Distances from the origin to the center of each sample and the distance from the origin to the solvent front have been provided.

Rf = (distance from origin to center of sample)/(distance from origin to solvent front) *answer may vary 0.4, 0.6

Highlight the amide group in acetanilide.

See quiz. Amide, an organic functional group characterized by a carbonyl group linked to a nitrogen atom, or a compound that contains this functional group

Draw the structure of acetanilide.

See quiz. C8H9NO

Purpose? The contents of the reaction flask were passed through a column of silica.

Separate the non-polar ether product from the polar by-products.

What is the major underlying principle of chromatography?

Separation will be achieved if one component adheres to the stationary phase more than the other component does.

The solubility of acetanilide is 0.53 g in 100 mL of ice-cold water, and 5.5 g in 100 mL of boiling water. What is the maximum percent recovery that can be achieved for the recrystallization of acetanilide from water?

Step 1) 5.5 g - .53 g = 4.97 g Step 2) % recovery = final mass/initial mass*100%

The gauche conformation of butane occurs when the dihedral angle between the C1-C2 bond and the C3-C4 bond is 60°. There is steric strain in the molecule because of the proximity of the two methyl groups. Would the steric strain in this molecule increase or decrease if the C1-C2-C3 bond angle (and the C2-C3-C4 bond angle) was increased to more than 109.5° ? *There is a picture but it doesn't matter because the question is not specifically asked about it.

Steric strain will decrease because groups are moving further apart

Recrystallization requires the material that is to be purified be a solid.

TRUE

T/F - Sodium hydroxide can cause severe damage to skin and eyes.

TRUE

Statements describing requirements for suitable solvents for recrystallization are listed below. Sort these requirements as either true or false.

TRUE: -The solvent should not chemically react with the compound -The solvent should dissolve the compound while hot -The solvent should not dissolve the compound when cold -The solvent should either dissolve the impurities at all FALSE: -The solvent should not dissolve the compound while hot -The solvent should chemically react with the compound -The solvent should dissolve the compound while cold

The following statements are true and correct:

The Rf value is defined as the ratio between the distance the spot moved and the distance the solvent moved. Rf is dependent on polarity. Polar compounds will have lower Rf values than nonpolar compounds under the same developing conditions. The more polar the solvent, the higher the Rf values. Rf values should be kept in the range of 0.2 to 0.8 for the most effective separation when more than one compound is present in the sample.

List the seven procedural steps, from start to finish, that are required to perform a thin layer chromatographic separation.

The TLC chamber is set up first to allow the solvent vapor to fill the chamber before the separation begins. The TLC plate is marked gently with a pencil near the bottom. A small spot of sample solution is delivered over the pencil mark. The TLC plate is stood upright in the developing solvent, and the lid is replaced to allow the solvent vapor to fill the chamber. The TLC plate must be removed before the solvent front reaches the top of the plate. The position of the solvent front must be marked before the TLC plate dries, because it may not be visible when dry. Most organic substances don\'t have any appreciable color. It may be necessary to spray the TLC plate with a dye, or to view the plate under UV light in order to reveal the spot. The Rf value can be determined once the distance traveled by the spot and the distance traveled by the solvent front have been measured.

In the presence of hydrochloric acid, 3,7-dimethyl-3-octanol is converted to 3-chloro-3,7-dimethyloctane via an SN1 mechanism. SN1 and E1 mechanisms are usually in competition with each other. Why, in this case, is the elimination product not observed?

The alkene formed by any E1 reaction would react with HCl to form the same product as the substitution reaction

What is a eutectic?

The composition of a mixture of 2 components that generates the lowest possible melting point.

Which of the following statements best describes eutectic composition?

The composition of a mixture of two components that generates the lowest possible melting point. (A eutectic composition occurs when a single composition of a two component mixture melts at a temperature that is lower than either of the melting points of the two pure components.)

Which of the following is the most polar compound? a. acetone b. acetic acid c. water d. toluene e. cyclohexane

c

When comparing melting temperature ranges of pure and impure samples, which of the following statements describes the melting temperature range of an impure sample? For an impure substance,

The melting point is lower than that of a pure sample.

For an impure substance,

The melting point is lower than that of a pure sample. (The addition of impurities to a substance causes a depression and broadening of the melting point.)

For a pure substance,

The melting temperature range is narrower than that of an impure sample.

In order to perform a bromine test on a compound, it must be treated with a dilute solution of bromine. Which of the followingresults will indicate the presence of an alkene.

The reddish color of the bromine will disappear.

Which of the following statements best describes density?

The ratio of a substance's mass to its volume, measured in g/mL and also equivalent tog/cm3.

Which of the following statements best describes density? The ratio of a substance\'s mass to its volume, measured in g/mL and also equivalent to g/cm3. The mass that a mole of substance has, measured in g/mol The amount of substance dissolved in a liquid, measured in mol/L. The mass of substance dissolved in a liquid, measured in g/mL.

The ratio of a substance\'s mass to its volume, measured in g/mL and also equivalent to g/cm3.

List the procedural steps, from start to finish, that are required to convert 2-naphthol and allyl bromide into allyl 2-naphthyl ether.

The reaction is performed on a small scale by mixing the alcohol, the haloalkane, and the phase transfer catalyst in a conical vial. Sodium hydoxide (base) is added to initiate the reaction. The reaction flask is covered and stirred to conduct reaction to prevent evaporation of the solvent. The progress of the reaction is monitored by TLC so that no time is wasted. The reaction solution is then dried over calcium chloride to remove any remaining water. The product is purified by column chromatography and collected by evaporation.

Both Br2 and HCl undergo electrophilic addition to alkenes. Why is Br2 used as a test for unsaturation instead of HCl?

The reaction with bromine can be followed because of a visible loss of color.

What error is induced if the bulb of the thermometer, or the thermocouple, is too high in the distillation apparatus?

The recorded boiling point will be lower than actual because the bulb is not exposed to the hot vapor.

A mixture of benzoic acid and benzocaine in dichloromethane solution were separated by solvent extraction first with sodium hydroxide, and then with hydrochloric acid. Drag and drop the chemical wastes generated in this reaction into the appropriate container.

The sodium hydroxide solution should go to the Acidic Aqueous waste container. The sodium hydroxide solution should go to the Basic Aqueous waste container. The wash acetone should go in the Wash Acetone container. The dichloromethane should go in the Dichloromethane, Benzamide waste container. The pH paper and benzoic acid should go to the Used Filter Paper, Solid Benzoic Acid and Solid Benzocain Crystals waste container.

In regard to the TLC plate you will be using in lab, which statement is true?

The stationary phase is more polar than the mobile phase.

How is it possible to separate two liquids with the exact same boiling point by gas chromatography when it cannot be done by fractional distillation? -the use of a non-polar GC column will separate liquids based on differences in volatility -increasing the length of the GC column will allow the more volatile component to elute faster -decreasing the diameter of the GC column will allow the more volatile component to elute faster -the use of a polar Gc column will separate the liquids based on differences in polar interactions and volatility

The use of a polar GC column will separate the liquids based on differences in polar interactions and volatility

How is it possible to separate two liquids with the exact same boiling point by gas chromatography (GC) when it cannot be done by fractional distillation?

The use of a polar GC column will separate the liquids based on differences in polar interactions and volatility.

List the procedural steps, from start to finish, that are required to perform a chemically active solvent extraction of a three-component mixture composed of benzoic acid, benzocaine, and a neutral organic molecule all dissolved in dichloromethane.

This chemically active liquid-liquid extraction is used to separate a weakly acidic component from a weakly basic component. The solid mixture is dissolved in dichloromethane, placed in a separatory funnel, and extracted with concentrated hydrochloric acid. (The benzocaine is converted into a water-soluble salt) Water is added to dissolve the brown emulsion that forms between the two layers. The aqueous layer is separated from the organic layer, placed in an Erlenmeyer flask and basified to cause precipitation of the benzocaine. The dichloromethane layer is placed back in the separatory funnel, and shaken with sodium hydroxide solution. (Benzoic acid is converted into a water-soluble salt). The white gel-like emulsion is dissolved by adding water. The basic aqueous layer was separated into an Erlenmeyer flask and acidified to cause the precipitation of the benzoic acid. The solids are collected by filtration. The full procedure is listed in the lab manual.

Why are the vials placed into the centrifuge in pairs, 180 degrees apart?

To avoid dangerous vibration due to imbalance

Purpose? The reaction was stirred at a moderate, not rapid, pace.

To avoid making the reaction mix become an emulsion.

Why should you not rinse the syringe with acetone, but instead rinse it with the sample?

To avoid the introduction of a spurious peak into the GC trace

Purpose? Solid sodium hydroxide was added to 2-naphthol.

To deprotonate alcohols to become good alkoxide nucleophiles.

Why must you wait for the second peak to be on the rise before beginning its collection

To preserve the purity of the sample because there is a lag between being detected and being eluted

...

To remove insoluble solid impurities.

When is recrystallization NOT a suitable method to purify an organic material?

When the organic material is a LIQUID

When is recrystallization not a suitable method to purify an organic material?

When the organic material is not a solid.

what do molecular orbitals describe?

a region of space around a molecule where an electron is likely to be found, instead of just an atom (i.e. delocalization)

In the oxidation reaction of a tertiary alcohol, the alcohol is converted to:

a tertiary alcohol is not oxidized

During Thin Layer Chromatography, what method is typically used to apply the dilute sample of solution to a TLC plate?

a thin glass spotter or capillary tube

cis 1,3

a,a or e,e

trans 1,4

a,a or e,e

cis 1,4

a,e or e,a

trans 1,3

a,e or e,a

(Recrystallization of Acetanilide) There are four major methods of purification in the chemistry laboratory. Which of the following techniques are included in the four most common methods for separation and purification? Select all that apply. a. Recrystallization b. Distillation c. Sublimation d. Extraction

abd

diameter of a typical atom

about 200 picometers (pm)

Eugenol

acetyl coenzyme A precursor acetogenin

BB undergoes what three color phases

blue - basic, 7.6 and higher green - neutral yellow - acidic, 6 or lower

Which reagent is not an oxidizing agent? a. NaOCl b. KMnO4 c. CaSO4 d. K2Cr2O7 e. CrO3

c

Butyl butyrate, an ester, differs from p-dioxane, an ether, by showing a strong infrared absorbance at: a. 3500 cm-1 b. 2950 cm-1 c. 2250 cm-1 d. 1745 cm-1 e. 1212 cm-1

d

safety precaution for NaOH

damage eyes

electronegativity (EN)

describes an atom's ability to attract e⁻ to itself in a covalent bond (arbitrary scale that accounts for bond polarity)

For recrystallization, rapid cooling gives the best crystals.

false

solid acetanilide crystals and filter paper

filter paper

wash acetone waste

glassware rinse acetone

A three dimensional representation of butane is shown on the left. Translate the information about the conformation of butane into its Newman projection on the right, and determine if this conformation represents a local energy minimum or a global energy minimum.

global energy minimum. staggered: H (top/right) Ch3 (left) on front carbon

functional group: alkene

has a C=C

functional group: alkyne

has a C≡C

equatorial position of cis-1,2-dimethylcyclohexane

in this conformation more than 99% of time at room temperature because it's much more stable

cyclohexane boat form

highest energy conformation -take one side of chair and bring it up to create flag-pole interaction between top two H -free of angle strain, but has some torsional strain -28 kJ/mol more energy than chair form

butane syn eclipsed conformation

highest energy conformation when the two methyl groups are 0° from each other (combination of torsional and steric strains)

what determines the number of covalent bonds an atom forms?

how many additional valence e⁻ it needs to reach a noble gas configuration

An over the counter headache pill was crushed, extracted into ethanol / dichloromethane, and then analyzed by TLC on silica using ethyl acetate as an eluent. The pill was shown to contain: acetaminophen, aspirin, and ibuprofen. Which is the least polar molecule? Rank the molecules interms of their Rf (highest to lowest).

ibuprofen ibuprofen, aspirin, acetaminophen

alkane nomenclature: 20 C

icosane

ground state electron configuration

lists orbitals occupied by an atom's electrons when they are in the lowest energy orbitals

first order rate expression

ln [RCl]0/[RCl]t=kt

what is the equation we used to plot the data points

ln(Vinfinity-Vt)/(Vinfinity-Vt) = kt

staggered conformation

lowest energy and most stable conformation where all 6 C-H bonds are as far apart as possible

interesting compounds with regards to organic acids/bases

methanol and acetone can act as acids when they donate a proton, but as bases when their oxygen atom accepts a proton

what does a bigger dipole moment mean?

molecule is more polar

cyclohexane

most common cyclic ring encountered in nature -chair, half chair, twist boat, and boat conformations.

cyclopropane

most strained of all rings because of angle strain (60°)and torsional strain (all C-H are eclipsed) -planar structure -highest energy cycloalkane

EN atoms

most: red (N, O, F, Cl, Br) intermediate: yellow least: green

what does n-C₄H₁₀ mean?

n denotes normal (straight-chain) butane

most common organic bases?

nitrogen containing compounds. involved in almost all metabolic pathways

another name for a Lewis base

nucleophile

what characterizes a good solvent for this reaction

one that is polar enough to dissolve the KOH but organic enough to dissolve the alkyl halide

Lewis Theory (1918)

organic chemicals form covalent bonds from sharing electrons because it's lower energy and more favorable

Brønsted-Lowry base

proton (H⁺) acceptor

Brønsted-Lowry acid

proton (H⁺) donor

what happens in the fast step

proton is lost

fast step

protonation

write the rate expression for an Sn1 reaction of R-Cl

rate = -k[RCl]

node

region of zero electron density that separates p orbitals (one regions separated is + and the other is -)

slow step

removal of water

what might molecules do to get the lowest energy?

sacrifice one of the three strains

Compared to dichromate oxidizing agents, hypochlorous acid is _____________.

safer, less expensive and environmentally friendly

stereoisomers

same atomic order, but different three dimensional orientation

conformational isomers

same molecular formula, but differ in arrangements of atoms that result from bond rotation

constitutional isomer

same molecular formula, but differ in how their atoms are arranged in chains (e.g. pentane, isopentane, neopentane; all C₅H₁₂)

cycloalkanes

saturated cyclic hydrocarbons (aka alicyclic compounds)

how are orbitals grouped?

shells of increasing size and energy 1st: 2 e⁻ (one 1s) 2nd: 8 e⁻ (one 2s and three 2p) 3rd: 18 e⁻ (one 3s, three 3p, and five 3d)

resonance hybrid

single unchanging structure, which is a composite of the resonance structures

fastest SN1 reaction occurs in

tertiary alkyl halides; doesnt occur/slowest in methyl halides

A separatory funnel contains the two immiscible liquids water and tetrahydrofuran. Use the given densities to determine which layer is on top and which is on the bottom in the binary mixture.

tetrahydrofuran : top water: bottom

What would happen if the chloride abstracted the proton instead of water?

the HCl would react with the water to form hydronium and a chloride ion

which cyclohexane substituent should be in the e position?

the bulkier group

eclipsed conformation

the highest energy and least stable conformation where all 6 C-H bonds are as close as possible

cause for the torsional strain?

the interaction between C-H bonding orbitals on one C with anti bonding orbitals on the adjacent C.

at what rate is the acid form

the same rate as the alcohol is formed

what is organic chemistry?

the study of carbon containing compounds. all living things are made of organic chemicals (i.e. proteins, DNA, etc).

cyclopentane

theoretical planar would have very high torsional strain -actual conformation is nonplanar which reduces torsional strain (5th C is puckered like envelope fold)

1-phenyl-1-chloroethane precaution

treat as lachymator

alkane nomenclature: 11 C

undecane

a strong acid has a...

weak conjugate base

larger Ka

weaker acid

a weak acid has a...

weaker conjugate base

banana bond

what occurs in cyclopropane. sp³ orbitals are bent and don't overlap efficiently

Acetanilide was recrystallized from a minimum amount of hot water, then collected using vacuum filtration. Identify where the waste generated by this process should go. Drag and drop the chemical wastes generated in this reaction into the appropriate container.

Dissolved in Acetanilide in Water from Recrystallization: filtrate Solid Acetanilide Crystals and Filter Paper: filter paper Halogenated Organic Waste: none Wash Acetone Waste: glassware rinse acetone Glass Waste: melting point capillary

What should a student do if there is a fire in the laboratory?

Do not panic, evaluate the situation, and then alert your TA for help.

torsional strain

eclipsed conformation creates the extra energy on neighboring atoms

acid strength: resonance

electron density is pulled into molecule and the basic sites are not as reactive

Valence Bond Theory

electrons are paired in overlapping orbitals and are attracted to the nuclei of both atoms

another name for a Lewis acid

electrophile

Under the reaction of limonen with excess Br2, what mecanism is in effect?

electrophilic addition

cyclohexane twist boat form

energy minimum between half chair and boat forms -nearly free of angle strain -contains torsional strain and steric strain, but less than boat form -23 kJ/mol more energy than chair form

butane gauche conformation

energy minimum in the staggered conformation that is higher in energy than the anti conformation even though it has no eclipsing interactions (3.8 kJ/mol higher)

adding mono substituted substituents to cyclohexanes

equatorial conformation of methyl cyclohexane is more stable than axial by 7.6 kJ/mol

what is another molecule that can react with the carbocation intermediate

ethanol, CH3CH2OH

angle strain

expansion or compression of bond angles away from the most stable

alkanes

fairly unreactive compounds with C-C single bonds and C-H bonds only (i.e. saturated with H) (aka aliphatic compounds)

For hot vacuum filtration, the filter paper should be completely dry when pouring the hot solution into the Buchner funnel to filter.

false

dissolved acetanilide water from recrystalization

filtrate

solvolysis reactions

first order substitution reactions in which the solvent acts as the nucleohile and the reaction rate is independent of the solvent concentration

acidity constant (Ka)

gives the exact strength of a given acid HA (concentration of products/reactants)

functional groups

group of atoms/bonds within a molecule that possess predictable chemical behavior 1. C with multiple bonds 2. C bonded to an EN atom 3. C=O "carbonyl" containing compounds

Identify the atoms that participate in 1,3-diaxial interactions interactions in the shown conformation of trans-1,2-dimethylcyclohexane. How many total 1,3-diaxial interactions are present in this molecule? -3d structure has equatorial methyl groups

-0

Identify the gauche interactions between methyl groups in the shown conformation of trans-1,2-dimethylcyclohexane. How many gauche interactions are there between methyl substtuents of this molecule? *2D and 3D structure is given *same 2D as last question but different 3D (methyls are equatorial)

-1 -Explanation: In the diequatorial conformer of trans-1,2-dimethylcyclohexane, the methyl groups are separated by a torsion angle of 60°. This gauche interaction destabilizes the molecule by 3.8 kJ/mol (0.9 kcal/mol).

Identify the atoms that participate in 1,3-diaxial interactions in the shown conformation of cis-1,2-dimethylcyclohexane. How many total 1,3-diaxial interactions are present in this molecule? -methyl groups are on the same face but there is only one axial methyl

-2

Which of the following is an indication of a positive test for the permanganate test (Baeyer's test)?

-A brown precipitate of manganese dioxide is formed. -The deep purple color of the reagent disappears.

Which of the following is an indication of a positive test for the permanganate test (Baeyer\'s test)?

-A brown precipitate of manganese dioxide is formed. -The deep purple color of the reagent disappears.

During the recrystallization of an impure solid sample of acetanilide, the sample is dissolved in hot water then filtered while hot. The filtrate is allowed to cool and the mixture is filtered a second time. What should a student do if they observe an oil forming as the solution cools?

-Add a small amount of additional water to the flask containing the oil. -Once the oil has dissolved, allow the solution to cool slowly. -Reheat the solution gently until the oil dissolves.

Which of the following statements are true concerning azeotropes?

-An unknown liquid that boils at a constan temperaure could be an azeotrope. -The boiling point of an azeotrope is lower than either of the pure substance it is composed of.

skeletal structures

-C atoms aren't shown (assumed to be at each intersection and ends of lines) -H bonded to C aren't shown -atoms other than C and H are shown -groupings are sometimes inverted to make bonding connections clearer

Which of the following is true of lab report due dates and the submission location?

-Due dates for lab reports are found on the syllabus. -Lab reports are to be placed in one of the organic labs report cabinets in the slot labelled with your TA\'s name on it.

which of the following statements about infrared spectroscopy is not true? -IR is non-destructive -IR can be used to analyze almost any kind of sample -IR can detect impurities within a sample -IR is good for detecting and identifying functional groups of a sample

-IR can be used to analyze almost any kind of sample

Which of the following are true statements which apply when using weigh boats in laboratory?

-In some cases, the weigh boat will be use by all students -The weigh boat must be tared before adding new material. -A paper towel should not be used to transfer product out of a weigh boat. - The balances in lab can be zeroed out with a weigh boat on the balance. -Plastic weigh boats can help prevent spillage when weighing liquids into a beaker.

If a student spills a chemical on their skin or clothing, what should they do?

-Inform their Teaching Assistant immediately. -Wash with soap and water immediately.

What safety rules apply to the organic chemistry laboratory?

-Keep all backpacks and coats off the floor and out of the aisles. -Follow the experimental procedures given. No unauthorized experiments. -Wear proper clothing at all times. -Do not conduct any experimental procedures unless the Teaching Assistant is present.

Which of the following statements are examples of academic misconduct?

-Observing your lab partner copying answers or duplicating lab reports and keeping this action to yourself. -Attempting to receive credit for work performed by another, including papers obtained fully or in part from individuals or other sources. -Acquiring answers for any assigned work from any unauthorized source.

In which of the following ways is the use of an infrared spectrophotometer fitted with an ATR sample advantageous over a beam-through-sample spectrophotometer? Select all answers that apply.

-The ATR crystal is not degraded by the presence of water. The same ATR sample holder may be used for liquid samples and solid samples.

Which of the following statements about melting point determination are true?

-The melting point is a physical measure of the forces holding the material into its crystal lattice. -The lower limit of the melting temperature range occurs when the first crystal starts to melt. -The upper limit of the melting temperature range occurs when the last remaining crystal melts.

What are true statements which apply to TLC?

-The solvent level should be below the spots. -Do not allow the edges of the plate to touch the filter paper. -Do not allow the solvent front to get 5 to 10 mm from the top of the plate. -When the solvent front has reached the correct height, remove from the chamber and immediately draw a line at the new solvent front. -TLC data is interpreted in terms of Rf values.

Which of the following are requirements for a suitable solvent when performing recrystallization?

-The solvent should not dissolve the compound when cold. -The solvent should either dissolve the impurities at all temperatures or not at all.

Which of the following statements about the collection of a GC trace is true?

-The staitonary phase is a very high-boiling liquid absorbed onto fire brick. -The amount of sample detecte is proportional to the peak area.

A mixture of two miscible volatile liquids is distilled. Which of the following statements are true concerning the boiling point of the distillate?

-The temperature range should start being recorded from when the liquid first starts to boil. -The temperature range should be recorded until right before the dramatic drop in temperaure. -If the range is within 2 degrees C, then the distillate can be considered pure.

A 0.7 mL mixture of pentanol and heptanol are separated and collected using preparative gas chromatography on a GC fitted with a polar column and a TCD detector. During the separation, why are the injection port and detector heated to a higher temperature than the column? Select all that apply.

-The wire in the thermal conductivity detector needs to be cooled by the eluent in order to register a signal. -A heated injector creates flash vaporization which allows separation at temperatures lower than the boiling point of the sample.

For a successful TLC experiment, you need to pay attention to the details. From the list of instructions and tips below, select the correct items.

-Use a micropipet or glass capillar to put a small amount of the sample solution on the starting line. -The solvent level in the chamber should be lower than the starting line where you spot the samples. -Use only a plain pencil to draw a starting line and mark the compounds\' spots. Never use a pen or marker! -Cover the developing chamber with a watch glass. -Once the solvent front is getting close to the top of the plate, remove the plate and mark the solvent front. -Do not disturb the developing chamber, do not move it or carry around. -Do not permit the solvent to rise to the very top of the TLC plate.

special properties of carbon

-can share 4 valence electrons and form 4 strong covalent bonds -can bond to one another forming chains and rings -exists in nature in 2 stable isotopes (carbon-12 and carbon-13)

two kinds of organic acids

-contain a hydrogen atom bonded to an electronegative oxygen atom, O-H (e.g. methanol, acetic acid) -contain a hydrogen atom bonded to carbon atom next to a C=O bond, O=C-C-H (e.g. acetone)

There are four major methods of purification in the chemistry laboratory. Which of the following techniques are included in the four most common methods for separation and purification?

-distillation -chromatography -extraction

problem with conformations of ethane?

-do not observe perfectly free rotation (99%:1% ratio of time spent in staggered and eclipsed conformations) -barrier to rotation can be seen graphically with energy maxima and minima

In the laboratory, what should a student be able to locate at all times?

-fire extinguishers -eyewash stations -safety shower -laboratory exits

What situations should students report to their Teaching Assistant immediately?

-if there is a fire in the laboratory -if there is a chemical spill

acid strength: periodic table trends

-in a period: acidity increases to the right (because stronger EN stabilizes the atom) -in a group: acidity increases going down (larger orbitals cause the electron density to be more spread out. therefore, there's less electron, electron repulsion)

When keeping a laboraory notebook, a student should always:

-mark out any unused portion of the page to indicate the conclusion of the day\'s work if there is no additional work to be done with the experiment. -write on the numbered, duplicated notebook pages that are included in the back of the lab manual.

naming alkanes...things to remember

-when counting the longest C chain, maximize branching -if equal distance from both ends of the first branch, then go off second branch point -use prefixes di, tri, and tetra for multiple substituents (don't alphabetize according to prefixes) -name complex substituents as their own compounds

Identify the gauche interactions between methyl groups in the shown conformation of trans-1,2-dimethylcyclohexane. How many gauche interactions are there between methyl substituents in this molecule? *structure 3D and 2D given (methyls are axial)

0 -Explanation: In the diaxial conformer of trans-1,2-dimethylcyclohexane, the methyl groups are separated by a torsion angle of 180°. There are no gauche interactions in the molecule shown.

The retention factor, or Rf, is a number that describes the position of a spot on a chromatography plate relative to the position of the solvent on the chromatography plate. What are the minimum and maximum values of Rf?

0 and 1.

("Who Has My Compound?") The retention factor, or Rf, is a number that describes the position of a spot on a chromatography plate relative to the position of the solvent on the chromatography plate. What are the minimum and maximum values of Rf?

0,1

The essential oil found in cloves, eugenol, can be isolated by steam distillation because it is insoluble in water and has a measurable vapor pressure at 100 °C even though it has a much higher boiling point than water. Use data from the table to calculate the mole fraction of eugenol in the distillate.

0.0053

The image below shows thin-layer chromatography results for two samples, A and B. Calculate the Rf values for both samples. Distances from the origin to the center of each sample and the distance from the origin to the solvent front have been provided. Distance to center of sample A= 2.8 cm Distance to center of sample B= 4.2 cm Distance from origin to solvent front= 6.8 cm

0.4,0.6

Identify the gauche interactions between methyl groups in the shown conformation of cis-1,2-dimethylcyclohexane. How many gauche interactions are there between methyl substituents on this molecule? *3D and 2D structure given

1 -Explanation: In cis-1,2-dimethylcyclohexane, the methyl groups are separated by a torsion angle of 60°. The steric repulsion caused by this gauche interaction destabilizes the molecule by 3.8 kJ/mol (0.9 kcal/mol).

two events for the development of the chemical bonding theory

1. 1858: Kekulé and Couper independently observed that carbon forms 4 bonds (still 2D though). Kekulé also claimed they can form rings 2. 1874: van't Hoff and Le Bel claimed carbon forms 3D tetrahedral molecules

The infrared spectrum displays the wavelengths at which specific functional groups absorb energy. Match the functional group to the region of the spectrum that it is most likely to absorb energy. 1. O-H alcohol 2. C=O aldehyde 3. C=C alkene

1. 4000-3000 cm-1 2. 1800-1640 cm-1 3. 1600 cm-1

List the procedural steps, from start to finish, that are required to perform a dehydrohalogenation of 3-chloro-3,7-dimethyloctane by ethanolic potassium hydroxide. All steps must be used.

1. Add 3-chloro-3,7-dimethloctane and ethanolic potassium hydroxide to a roun-bottom flask containing boiling chips. 2. Attach a claisen head and an air condenser with greased joints. 3. Heat under reflux on a heating mantle for twenty minutes. 4. Cool, and pour the reaction contents into a test tube containing water. 5. Transfer the organic layer into another test tube and wash with water three times. 6. Dry the organic layer over calcium chloride in a sample vial. 7. ilter the product through a cotton plug into a pre-weighed vial.

List the procedural steps, from start to finish, that are required to convert 1-chloro-1-phenylethane into 1-phenylethanol via SN1 solvolysis in water.

1. Add a few drops of bromothymol blue to a stirred solution of ethanol and water. 2. Add sodium hydroxide solution from a burette. 3. Add alkyl halide and start the timer. 4. Record the time it takes for the solution to turn green. 5. Repeat the process of adding aliquots of measured base, annd recording the time taken for a color change. 6. Heat on a steam bath above 50 degrees Celsius for 20 minutes. 7. Titrate the contents of the flask against NaOH, and record the volume.

Match the procedural step to its purpose by dragging each step in the written procedure for the oxidation of cyclohexanol to cyclohexanone into the appropriate box. 1. Generate the oxidizing agent. 2. Destroy the oxidizing agent. 3. Test for the presence of oxidizing agent. 4. Control the rate of reaction. 5. Dry the reaction produt.

1. Add bleach dropwise into a flask containing acetic acid. 2. Add sodium bisulfite solution. 3. Touch a drop of the reaction mix onto a piece of KI-starch paper. 4. Place the reaction flask in an ice-water bath. 5. Combine the organic layers over anhydrous potassium carbonate.

List the procedural steps, from start to finish, that are required to convert of 3,7-dimethyl-3-octanol to 3-chloro-3,7-dimethyloctane using hydrochloric acid in an SN1 reaction.

1. Add concentrated hydrochloric acid to alcohol in an Erlenmeyer flask. 2. Add a stir bar and stir the solution for 20 minutes. 3. Occasionally rinse the sides of the flask with an aqueous layer. 4. Transfer the mixture to a test tube and remove the lower aqueous layer. 5. Wash the organic layer with saturated sodium chloride solution followed by sodium carbonate solution. 6. Dry the organic layer over sodium chloride. 7. Filter the dried organic material into a clean pre-weighed vial.

List the procedural steps that are required to convert 2-naphthol and allyl bromide into allyl 2-naphthyl ether.

1. Fit a conical vial with a stirring vane and add 2-napthol, allyl bromide, and benzyltriammonium chloride in dichloromethane. 2. Add NaOH to the reaction flask. 3. Cover the reaction vial and stir. 4. Periodically stop the stirring, allow the layers to settle, and spot the organic layer on a TLC plate. 5. Remove the bottom layer and dry over CaCl. 6. Run the reaction solution through a silica chromatography column. 7. Evaporate dichloromethane solvent to dryness.

("Who Has My Compound?") TLC Procedure: 1. Add just enough developing solvent to cover the bottom 3 mm of the TLC chamber. Cover with a watch glass. 2. Make a pencil mark on the TLC plate 10 mm from the bottom. 3. Use a capillary to deliver a 2 mm diameter spot onto the pencil mark. 4. Stand the TLC plate upright in the chamber, and replace the lid. 5. Remove the TLC plate when solvent is near the top of the plate. 6. Gently mark the position of the solvent front using a pencil before the TLC plate dries completely. 7. Measure the distance that the spot and solvent have moved.

1. Add just enough developing solvent to cover the bottom 3 mm of the TLC chamber. Cover with a watch glass. 2. Make a pencil mark on the TLC plate 10 mm from the bottom. 3. Use a capillary to deliver a 2 mm diameter spot onto the pencil mark. 4. Stand the TLC plate upright in the chamber, and replace the lid. 5. Remove the TLC plate when solvent is near the top of the plate. 6. Gently mark the position of the solvent front using a pencil before the TLC plate dries completely. 7. Measure the distance that the spot and solvent have moved.

List the 7 procedural steps, from start to finish, that are required to form a thin layer chromatographic separation.

1. Add just enough developing solvent to cover the bottom 3 mm of the TLC chamber. Cover with a watch glass. 2. Make a pencil mark on the TLC plate 10 mm from the bottom. 3. Use a capillary to deliver a 2 mm diameter spot onto the pencil mark. 4. Stand the TLC plate upright in the chamber, and replace the lid. 5. Remove the TLC plate when solvent is near the top of the plate and mark the solvent front with a pencil before the TLC plate dries. 6. Mark the outline of the spots on the plate with a pencil. Unless the spots are colored, some visualization method will be needed. 7. Measure the distance that the spot and the solvent have moved.

List the procedural steps, from start to finish, that are required to separate and collect a two-liquid mixture using preparative gas chromatography.

1. Collect a vial of unknown mixture. Record its number and letter. 2. Inject te mixture into the numbered Prep GC instrument that matches the number on your sample vial. 3. Slip a collection tube over the lower exit ort of the Prep GC just after the first fraction begins to elute. 4. Remove the collection tube when the first peak is almost finished. 5. Add another collection tube, and take a center cut for next fraction. 6. Transfer the samples to conical sample vials by connecting the vials to collecting tubes. 7. Centrifuge both vials to collect the samples. Cap the vials.

Match the type of fire with the method used to extinguish it. 1. Small fire contained completely with a beaker. 2. Fire confined to small portion of clothing. 3. The entire room is on fire. 4. A large portion of your clothes is on fire.

1. Cover the flame with a watch glass or hard-back book. 2. Pat the fire out. 3. Sound the fire alarm and evacuate the building. 4. Use the safety shower or fire blanket.

List the procedural steps, from start to finish, that are required to perform a chemically active solvent extraction of a three-component mixture composed of benzoic acid, benzocaine, and a neutral organic molecule all dissolvved in dichloromethane.

1. Dissolve the solid three-component mixture in dichloromethane and place in a separatory funnel. 2. Add water to dissolve the brown emulsion between the layers. 3. Separate and collect the aqueous layer in a flask, then add base. 4. Place the dichloromethane layer back in the separatory funnel and extract it with 3 M NaOH. Allow layers to settle. 5. Add water to disolve the white gel-like emulsion. 6. Separate and collect the aqueous layer in a flask, and add acid. 7. Collect and dry the solids in both Erlenmeyer flasks by filtration.

Label the following statements as either true or false. 1. Silica is toxic. 2. Hexane is flammable. 3. Ethyl acetate is flammable. 4. Acetone is flammable. 5. It is acceptable to handle TLC plates with bare hands.

1. F 2. T 3. T 4. T 5. F

Label the following as either true or false. 1. NaOH can cause severe damage to the skin and eyes 2. Lachrymators like allyl bromide are specifically dangerous because of their explosion hazard. 3. The primary risk associate with dichloromethane is its flammability. 4. Unused allyl bromide can be disposed of in the aqueous waste. 5. Gloves and goggles are not required when handling sodium hydroxide.

1. T 2. F 3. F 4. F 5. F

List the procedural steps, from start to finish, that are required to convert cyclohexanol to cyclohexanone.

1. Mix cycylohexanol and acetic acid in an Erlenmeyer flask 2. Add bleach dropwise into the flask. 3. Maintain the reaction temperature between 40 and 45 on a steam bath. 4. Remove unused bleach wih sodium bisulite solution. 5. Add drops of 6M NaOH until solution is pH 6. Place reaction in separatory funnel, extract with dichloromethane. 7. Dry the dichloromethane layer over potassium carbonate. 8. Decant from the potassium carbonate and collect by distillation.

Match the procedural step for its purpose for the chemically active solvent extraction of a three-component mixture composed of benzoic acid, benzocaine, and a neutral organic molecule all dissolved in dichloromethane. 1. To recover a mixture in case a stopcock leaks 2. To dissolve the emulsion due to the benzocaine salt exceeding its solubility. 3. To precipitate the benzocaine. 4. To handle the separatory funnel properly.

1. Place a beaker below the separatory funnel. 2. Add water to the separatory funnel that contains an acidified three-component mixture in dichloromethane. 3. Add base to the aqueous acidic layer mixture. 4. Cradle the inverted separatory funnel in the palm of the hand and hold the stopper between the fingers of the same hand.

List the procedural steps, from start to finish, that are required to perform a steam distillation of limonene from orange peel.

1. Place citrus peel into a preweighed round bottom flask. 2. Add water until the level is past the midpoint of the flask. 3. Attach a ondenser and receiving flask with greased joints, then distill the mixture. 4. Add ethyl acetate to the receiving flask to extract the droplets of oil. 5. Separate the layers, and dry the organic layer over calcium chloride. 6. Filter off the drying agent, and then remove the ethyl acetate solvent by microdistillation. 7. Collect and weigh the residue of pure limonene.

List the procedural steps that are required to perform a steam distillation of limonene from orange peel.

1. Place citrus peel into a preweighed round bottom flask. 2. Add water until the level is past the midpoint of the flask. 3. Attach a condenser and receiving flask with greased joints, then distill the mixture. 4. Add ethyl acetate to the receiving flask to extract the droplets of oil. 5. Separate the layers, and dry the organic layer over calcium chloride. 6. Filter off the drying agent, and then remove the ethyl acetate solvent by microdistillation. . 7. Collect and weigh the residue of pure limonene.

List the procedural steps, from start to finish, that are required to perform an extraction of eugenol from a solution of clove oil in dichloromethane.

1. Place the dichloromethane solution of clove oil into a separatory funnel. 2. Add sodium hydroxide solution. Separate and collect the aqueous layer. 3. Acidify the aqueous layer with hydrochloric acid. 4. Extract the acidic solution into dichloromethane. Collect the organic layer. 5. Dry the dichloromethane solution over calcium chloride. 6. Remove the dichloromethane solvent by microdistillation. 7. Collect and weigh the residue of pure eugenol.

List the procedural steps that are required to perform an extraction of eugenol from a solution of clove oil in dichloromethane.

1. Place the dichloromethane solution of clove oil into a separatory funnel. 2. Add NaOH solution, Separate and collect the aqueous layer. 3. Acidify the aqueous layer with HCl. 4. Extract the acidic solution into dichloromethane. Collect the organic layer. 5. Dry the dichloromethane solution over calcium chloride. 6. Remove the dichloromethane solvent by microdistillation. 7. Collect and weigh the residue of pure eugenol.

List the procedural steps, from start to finish, that are required in the recrystallization of acetanilide.

1. Place the finely divided mixture and a boiling chip into an Erlenmeyer flask on a steam bath. 2. Add the minimum amount of hot water to dissolve the solid. 3. Rapidly filter the hot solution through a pre-warmed funnel. 4. Wash the filter with hot solvent and transfer the filtrate to a clean flask. 5. Allow the filtrate to cool slowly, then cool in an ice bath to form precipitation. 6. Vacuum filter the cold suspension. 7. Air dry the purified solid on the filter.

"Who Has My Compound?" M.P. Determination Procedure: 1. Press the open end of a capillary tube into the solid sample. 2. Invert the tube and tap gently to move the solid to the bottom of the capillary. 3. Place the loaded tube into the hole in the melting point apparatus, and heat at 10 degrees per minute. 4. Observe the material through the complete melting process to get a rough estimate of the melting point range. 5. Turn off and allow to cool by 15 degrees. 6. Replace the existing tube with a new sample. 7. Heat at 2 degrees per minute through the expected range.

1. Press the open end of a capillary tube into the solid sample. 2. Invert the tube and tap gently to move the solid to the bottom of the capillary. 3. Place the loaded tube into the hole in the melting point apparatus, and heat at 10 degrees per minute. 4. Observe the material through the complete melting process to get a rough estimate of the melting point range. 5. Turn off and allow to cool by 15 degrees. 6. Replace the existing tube with a new sample. 7. Heat at 2 degrees per minute through the expected range.

List the 7 procedural steps that are required to perform an accurate melting point determination.

1. Press the open end of a capillary tube into the solid sample. 2. Invert the tube and tap gently to move the solid to the bottom of the capillary. 3. Place the loaded tube into the hole inthe melting point apparatus, and heat at 10 degrees per minute. 4. Observe the material through the complete melting process to get a rough estimate of the melting range. 5. Turn off and allow to cool by 15 degrees. 6. Replace the existing tube with a new sample. 7. Heat at 2 degrees/minute through the expected range.

What effect would each of the following changes to the conditions of a GC separation have on the retention time for a sample. 1. The amount of sample injected is doubled. 2. The carrier gas flow is increased. 3. The column temperature is decreased.

1. Retention time increases. 2. Retention time decreases. 3. Retention time increases.

Label the following statements as true or false: 1. If a student is asked to weigh out 3.0 g of a material, anything between 2.8 g and around 3.1 g will work fine. 2. If a student is asked for an arbitrary volume of 10 mL, then they must measure to precisely 10 mL. 3. For an ice bath, only use ice alone to assist in an even cooling and temperature transfer. 4. When assembling your apparatus, always start from the bottom up when using clamps. 5. Never grease the joints on common glassware setups.

1. T 2. F 3. F 4. T 5. F

Label the following statements as true or false: 1. No sandals or other open toed shoes allowed. 2. Shorts and skirts, as long as they are below the knee, are acceptable for laboratory. 3. You will be required to wear long pants in the laboratory at all times. 4. Sandals and open toed shoes are permitted as long as you wear socks underneath. 5. Long unrestrained hair is not permitted. 6. Wear enclosed safety goggles at all times in the lab. 7. Safety glasses are allowed in place of goggles if you do not wear contacts. 8. Loose-fitting or baggy clothing is not allowed in the laboratory.

1. T 2. F 3. T 4. T 5. T 6. T 7. F 8. T

Label the following statements as true or false. 1. Rf is dependent on polarity. 2. Polar compounds will have higher Rf values than nonpolar compounds under the same developing conditions. 3.Rf values should be kept in the range of 0.2 to 0.8 for the most effective separation when more than one compound is present in the sample. 4. The less polar the solvent, the higher the Rf values.

1. T 2. F 3.T 4.T

Label the following statements as true or false. 1. Hypochlorous acid is an oxidizing agent. 2. Concentrated acid is corrosive. 3. Methylene chloride is flammable. 4. Methylene chloride is a probably human carcinogen. 5. Pipets that contain only water can be disposed of in the trash.

1. T 2. T 3. F 4. T 5. F

Recrystallization is a common laboratory method to purify solids by dissolving them in hot solvent, filtering while hot, then allowing the filtrate to cool so that crystals form. Use the pop-up menus to label the following statements about the practical aspects of recrystallization as either True or False. 1. Use clamps to secure the filter flask to avoid tipping and unnecessary exposure to hot liquids or the solute. 2. Recrystallization requires the material that is to be purified be a solid. 3. For hot vacuum filtration, the filter paper should be completely dry when pouring the hot solution into the Buchner funnel to filter. 4. Recrystallization is the process of dissolving a solid material into a suitable solvent or mixture of solvents and allowing the material to crystallize from this solution. 5. For recrystallization, rapid cooling gives the best crystals.

1. T 2. T 3. F 4. T 5. F

Label the following statements concerning the care and use of a separatory funnel as either true or false. 1. The first step in utilizing a separatory funnel is t omake sure the funnel stopcock is closed and then carefully pour the liquid to be extracted into the funnel. 2.The stopcock can be used to vent excess pressure if either of the liquids are warm to the touch and has a low boiling point. 3. Students should throw away the first layer and acid washes. 4.Hold your thumb firmly over the hole in the top of the funnel during shaking. 5. If one is going to re-extract the upper layer with another volume of liquid, the upper layer can be left in the separatory funnel and fresh solvent added to the funnel.

1. T 2. T 3.F 4. F 5. T

Label the following statements as true or false. 1. The term reflux means heating a liquid to boiling and condensing the vapors back into the flask. 2. For the condenser, the bottom tube should be connected to the water source, the upper tube placed into the drain. 3. Regardless of the setup of the reflux apparatus, if liquid is circulated through a condenser, the cold water (inlet) should be directed at the top first. 4. One should allow the apparatus to completely cool before disassembling. 5. One should never use boiling chips to moderate reflux and prevent bumping.

1. T 2.T 3.F 4.T 5.F

Label the following statements as either true or false in relation to theoretical plates in a GC column. 1. The rate of heating affects the number of theoretical plates in the column. 4. Increasing the length of the column and packing the column with glass beads or rings are methods that produce more theoretical plates. 5. Rapid heating can drive heated vapor up the column, preventing the formation of an equilibrium that allows the lower boiling component to separate. As a result, this will increase the number of theoretical plates and increase the separation.

1. T 4. T 5. F

Match the procedural step to its purpose by dragging each step in the written procedure for the reaction of 2-naphthol with allyl bromide and a phase transfer catalyst in strong base into the appropriate box. 1. The non-polar ether product can be separated from the polar by-products. 2. Dissolved water is removed from the reaction mixture. 3. To avoid making the reaction mix become a emulsion ... 4. Dichloromethane solvent is highly volatile. 5. The time for the reaction to go to completion is kept under an hour.

1. The contents of the reaction flask were passed through a column of silica. 2. Enough calcium chloride to cover half the bottom of the flask was added. 3. The reaction was stirred at a moderate, not rapid, pace. 4. The reaction vial was stoppered before it was stirred. 5. Allyl bromide was used in excess.

Match the procedural step to its purpose by dragging each step in the written procedure for the SN1 conversion of 3,7-dimethy-3-octanol to 3-chloro-3,7-dimethyloctane by hydrochloric acid, with characterization test with silver nitrate solution. 1. To make the polar impurities less soluble in the organic layer. 2. To test for free chloride ions; an indication of a tertiary/benzylic carbocation. 3. To gently neutralize the acidic reaction. 4. To exclude water from the product and push the equilibrium to the right.

1. The organic layer was shaken with saturated sodium chloride solution. 2. A few drops of silver nitrate solution were added to the organic product 3. The organic layer was shaken with sodium bicarbonate solution. 4. The reaction was performed in concentrated hydrochloric acid, in which the organic halide is not soluble.

Match the procedural step to its purpose for the separation and collection of a two-component liquid mixture by preparative gas chromatography.

1. To avoid the introduction of a spurious peak into the GC trace ... do not rinse the syringe with acetone, rinse it with sample instead. 2. To avoid dangerous vibration due to imbalance ... vials are placed into the centrfuge in pairs, 180 degrees apart. 3. To avoid loss of sample ... the detector fitted to the Prep GC is a TCD not a FID. 4. To preserve the purity of the sample because there is a lag between being detected and being eluted ... wait for the second peak to be on the rise before beginning its collection.

Mixture melting point determination, solubility tests, and thin layer chromatography can be used to assess the purity and identity of a substance. Drag and drop each of the chemical wastes generated in this reaction into the appropriate container. 1. used melting point capillaries 2. contaminated paper towels 3. sodium bicarbonate solution 4. TLC solvent

1. broken glass 2. solid waste 3. aqueous waste 4. non-chlorinated organic waste

intermolecular forces

1. dispersion forces: due to uneven electron distributions causing a temporary dipole (stronger with more e⁻) 2. dipole-dipole forces: net dipole moment of the molecule 3. hydrogen bonds: when H is bonded to F, O, N atoms (stronger because small H has a highly localized positive charge and visa versa)

how to draw cyclohexane's chair conformation

1. draw 2 parallel lines downward and offset 2. draw topmost C above and to the right 3. draw bottom most C below and to the left 4. include axial (up and down) and equatorial (≈109° off existing bonds) H

four quantum numbers

1. principle quantum number (n): denotes size and energy (1→∞) 2. angular momentum number (l): denotes shape (l=0→n-1) 3. magnetic quantum number (m_l): denotes orientation (-l→+l) 4. spin quantum number (m_s): denotes electron in orbital (±1/2)

two ways to represent conformations

1. sawhorse (views C-C from an oblique angle) 2. Newman projection (views C-C directly end on with a circle representing the two C)

A mixture of hexane and octane were separated by a simple distillation and then tested for purity using gas chromatography. Identify where the waste generated by this process should go. 1. used kimwipe 2. hexane 3. octane 4. pasteur pipet 5. rinse acetone

1. solid waste 2,3. non-chlorinated organic waste 4. pasteur pipet 5. rinse acetone

requirements for suitable solvents for recrystallization

1. solvent should not chemically react with compound 2. solvent should dissolve the compound while hot 3. solvent should not dissolve comopund when cold 4. solvent should either dissolve the impurities at all temperatures of not dissolve the impurities at all

Label the following statements as either true or false: 1. The distance the spot moved is where the spot started to where it ended up. 2. The Rf value is defined as the ratio between the distance the spot moved and the distance the solvent moved. 3. Rf is not depenent on polarity. 4. The distance the solvent moved is where the spot started to where the solvent front ended up. 5. Polar compounds will have higher Rf values than nonpolar compounds uner the same developing conditions.

1.T 2.T 3.F 4.T 5.F

Label the following statements as true or false. 1. If a student needs to heat things over 100 °C, then one should use a heating mantle. 2.Magnetic stirrers provide sufficient agitation to prevent bumping. 3. Heating mantles should be plugged directly into an alternating current outlet. 4. Never drop a magnetic stir bar into a flask. Instead, tip the flask sideways and slide the stir bar in. 5. For maximum agitation potential, use stir bars and boiling chips together.

1.T 2.T 3.F 4.T 5.F

Considering that gauche interactions and 1,3-diaxial interactions both contribute 3.8 kJ/mol to the strain energy for a conformation, calculate the total strain energy for the shown conformation of cis-1,2-dimethylcyclohexane. What is the total strain energy of the molecule? *on the same face, one of the groups is axial, one is equatorial. **Remember Gauche=3.8 kj/mol, diaxial interactions=7.6 kj/mol

11.4 kj/mol (one gauche interaction and two 1,3-diaxial)

Considering that gauche interactions and 1,3-diaxial interactions both contribute 3.8 kJ/mol to the strain energy for a conformation, calculate the total strain energy for the shown conformation of trans-1,2-dimethylcyclohexane. What is the total strain energy of the molecule? *3d molecule has two axial methyl groups **Remember Gauche=3.8 kj/mol, diaxial interactions=7.6 kj/mol

15.2 kj/mol (four diaxial interactions)

None of the following molecules display much solubility in water at room temperature. However, two of the molecules display appreciable solubility in boiling water. Based on its structure, which molecule will be the least soluble in hot water? (PICTURES ON QUIZ)

2-Naphthol

None of the following molecules display much solubility in water at room temperature. However, two of the molecules display appreciable solubility in boiling water. Based on its structure, which molecule will be the least soluble in hot water?

2-naphthol

None of the following molecules display much solubility in water at room temperature. However, two of the molecules display appreciable solubility in boiling water. Based on its structure, which molecule will be the least soluble in hot water? salicylic acid 2-naphthol acetaminophen

2-naphthol

Which is less soluble in hot water, a compound with a single benzylic ring(Salicylic acid) or a compound wih two rings (2-naphthol)?

2-naphthol

What is the order of stability for carbocations

3 degree most stable, methyl least stable

Consider the reaction of 3.9 g cyclohexanol and an acid catalyst to yield 2.8 g cyclohexene. The molar mass of cyclohexanol is 100.16 g/mol and the molar mass of cyclohexene is 82.14 g/mol. Calculate the theoretical yield.

3.2 g

SI unit of debye (D)

3.336∙10⁻³⁰ C∙m

Considering that gauche interactions and 1,3-diaxial interactions both contribute 3.8 kJ/mol to the strain energy for a conformation, calculate the total strain energy for the shown conformation of trans-1,2-dimethylcyclohexane. What is the total strain energy in this molecule? *3d molecule has two equatorial methyls on separate faces **Remember Gauche=3.8 kj/mol, diaxial interactions=7.6 kj/mol

3.8 kj/mol (due to gauche)

orbital

3D region where the e⁻ is most likely to be found around a nucleus based on quantum mechanics (solution to a wave equation)

Identify the atoms that participate in 1,3-diaxial interactions in the shown conformation of trans-1,2-dimethylcyclohexane. How many total 1,3-diaxial interactions are present in this molecule? *2d and 3d (axial methyls) given

4

why should there be high yield of cyclohexene in this experiment

4 alpha hydrogens are all the same and so only yield one alkene product

A sample of an unknown liquid has a mass of 20.09 g, and a volume of 4.67 mL. What is the density of this liquid?

4.30 g/cm^3

The essential oil found in cloves, eugenol (shown below), can be isolated by steam distillation because it is insoluble in water and has a measurable vapor pressure at 100 °C even though it has a much higher boiling point than water. Use data from the table to calculate the mass percent of eugenol in the distillate.

4.63%

what did the second solution consist of

40% ethanol and 60% water

The infrared spectrum displays the wavelengths at which specific functional groups absorb energy. Match the functional group to the region of the spectrum that it is most likely to absorb energy. The scale is shown in wavenumbers, cm-1. Drag and drop the functional group onto the appropriate place on the spectrum. Consult your lab manual, as some of the regions overlap. regions given: 4000-3000, 2830-2680, 2200-2100,2000-1667,1800-1640,1600,1400-400 -groups given: alcohol, C=O aldehyde, C=C alkene

4000-3000=O-H alcohol 1800-1640=C=O aldehyge 1600=C=C alkene

What did the first solution consist of

50% ethanol - 50% water

functional group: arene

6 membered C ring (alternating C=C)

The solubility of acetanilide is 18.5 g in 100 mL of methanol at 0 °C, and 59.2 g in 100 mL of methanol at 60 °C. What is the maximum percent recovery that can be achieved for the recrystallization of acetanilide from methanol?

68.75%

The solubility of acetanilide is 12.8 g in 100 mL of ethanol at 0 °C, and 46.4 g in 100 mL of ethanol at 60 °C. What is the maximum percent recovery that can be achieved for the recrystallization of acetanilide from ethanol?

72.4%

A student was given a sample of crude acetanilide to recrystallize. The initial mass of the the crude acetanilide was 156 mg. The mass after recrystallization was 115 mg. Calculate the percent recovery from recrystallization.

73.7%

A student was given a sample of crude acetanilide to recrystallize. The initial mass of the the crude acetanilide was 166 mg. The mass after recrystallization was 125 mg. Calculate the percent recovery from recrystallization.

75.3%

Consider the reaction of 3.0 g cyclohexanol and an acid catalyst to yield 2.0 g cyclohexene. The molar mass of cyclohexanol is 100.16 g/mol and the molar mass of cyclohexene is 82.14 g/mol. Calculate the percent yield.

81%

During a solvent extraction, a student lost track of which layer was the aqueous layer and which was the organic layer. What simple, non-destructive test could be used ot determine which layer was which?

Add a little distilled water ot see which layer the water adds to.

During a solvent extraction, a student lost track of which layer was the aqueous layer and which was the organic layer. What simple, non-destructive test could be used to determine which layer is which? Obtain a sample of the solution in the separatory funnel and utilize NMR. Obtain a sample of the solution in the separatory funnel and utilize IR. Ask your instructor if you can perform a super critical extraction on your sample. Add a little distilled water to see which layer the water adds to.

Add a little distilled water to see which layer the water adds to.

Sodium hypochlorite and glacial acetic acid combine to make hypochlorous acid. Hypochlorous acid (HOCl) oxidizes cyclohexanol to cyclohexanone. At the end of the reaction, any excess hypochlorous acid must be neutralized. How is the neutralization of HOCl accomplished?

Add sodium bisulfite, NaHSO3.

Sodium hypochlorite and glacial acetic acid combine to make hypochlorous acid. Hypochlorous acid oxidizes cyclohexanol to cycylohexanone. At the end of te reaction, any excess hypochorous acid must be neutralized. How is the neutralization of HOCl accomplished?

Add sodium bisulfite, NaHSO3.

cycloalkane stability: ring strain

Adolf von Baeyer (1885) predicted that some cycloalkanes are unstable due to angle strain since the orbitals differ from 109° -compared the heats of combustion for the cyclic and normal chains

During the recrystallization of an impure solid sample of acetanilide, the sample is dissolved in hot water then filtered while hot. The filtrate is allowed to cool and the mixture is filtered a second time. Which of the following actions will increase the percent recovery of the acetanide solute?

After the first filtration, place the solution an ice-water bath for about 10 minutes.

Acetanilide was recrystallized from the minimum amount of hot water, and collected by vacuum filtration. Identify where the waste generated by this process should go.

Aqueous waste- filtrate Solid waste- filter paper Chlorinated organic waste- none Non-chlorinated organic waste- Rinse acetone Broken glass- melting point capillary

The following statements are true and correct when handling and spotting thin-layer chromatography plates: Always use a pencil to spot a TLC plate. Spot on the dull, not shiny side of the plate. Only touch the edges of the plate. Mark the plate before applying the sample. Spots should be 1 to 2 mm in diameter.

Always use a pencil to spot a TLC plate. Spot on the dull, not shiny side of the plate. Only touch the edges of the plate. Mark the plate before applying the sample. Spots should be 1 to 2 mm in diameter.

Acetanilide is an aromatic amide, it contains an aromatic π system, and an amide group. Highlight the amide group in acetanilide. Click on the molecule to rotate it in 3D. Click once on any atom to highlight it in blue.

Amides contain a three-coordinate nitrogen with an available lone-pair of electrons directly bonded to a carbonyl. The hydrogen attached to the nitrogen does not need to be highlighted in this question. The color scheme of the 3D molecule displays carbon atoms as grey, hydrogen atoms as white, oxygen atoms as red, and nitrogen atoms as blue.

A mixture of benzoic acid and benzocaine in dichloromethane solution were separated by solvent extraction first with sodium hydroxide, and then with hydrochloric acid. Which container should the chemical waste go to?

Aqueous Waste: sodium hydroxide solution, hydrochloric acid solution Solid Waste: used pH paper, benzoic acid Chlorinated Organic Waste: dichloromethane Non-Chlorinated Organic Waste: rinse acetone

Why is it good practice to perform a mixed melting point determination at two different ratios of unknown to known materials in the melting point capillary?

Because it is possible that one particular combination of materials generates a eutectic. (A eutectic is a mixture that produces a low, sharp melting point. It is possible to mistake the sharpness of a eutectic as a pure sample, and thus misjudge the temperature reading.)

The Williamson ether synthesis between 2-naphthol and allyl bromide in the presence of strong base and benzyltriphenylammonium chloride as a phase transfer catalyst in dichloromethane solution is known to proceed in reasonable yield. The need for a phase transfer catalyst would be removed if a polar aprotic solvent such as DMSO were used as a reaction solvent. Why is DMSO not used as a solvent for this reaction?

Because of risks associated with toxicity.

The Williamson ether synthesis between 2-naphthol and allyl bromide in the presence of strong base and benzyltriphenylammonium chloride as a phase transfer catalyst in dichloromethane solution is known to proceed in reasonable yield. The need for a phase transfer catalyst would be removed if a polar aprotic solvent such as DMSO were used as a reaction solvent. Why is DMSO not used as a solvent for this reaction?

Because of risks associated with toxicity.

The William ether synthesis between 2-napthol and allyl bromide in the presence of strong base and benzyltriphenylammonium chloride as a phase transfer catalyst in dichloromethane solution is know to proceed in reasonable yield. The need for a phase transfer catalyst would be removed if a polar aprotic solvent such as DMSO were used as a reaction solvent. Why is DMSO not used as a solvent for this reaction?

Because of the risks associated with toxicity.

The Williamson ether synthesis between 2-naphthol and allyl bromide in the presence of strong base and benzyltriphenylammonium chloride as a phase transfer catalyst in dichloromethane solution is known to proceed in reasonable yield. Why will the reaction fail to work if the solvent is switched to ethanol while retaining the same reactants, phase transfer catalyst, and base?

Because the base would deprotonate alcohol and create a second nucleophile.

The Williamson ether synthesis between 2-naphthol and allyl bromide in the presence of strong base and benzyltriphenylammonium chloride as a phase transfer catalyst in dichloromethane solution is known to proceed in reasonable yield. Why will the reaction fail to work if the solvent is switched to ethanol while retaining the same reactants, phase transfer catalyst, and base?

Because the base would deprotonate ethanol and create a second nucleophile.

Cyclohexane will give a positive result for which tests?

Bromine and permanganate

Limonene will give a positive result for which tests?

Bromine and permanganate

Translate the given conformer from the wedge-and-dash drawing into its Newman projection.

By inspecting the wedge-and-dash drawing, we know that the given molecule is in the eclipsed conformation: the wedge bond substituents, Br and CH3, are aligned; the dash bond substituents, Cl and H, are aligned; the line bond substituents, CH3 and H, are aligned. The orientation of substituents in the wedge-and-dash drawing must match that in the Newman projection, or else it would be a different conformer (i.e., do not rotate about the C-C bond). Thus, the aligned substituents of the wedge-and-dash drawing will eclipse each other in the Newman projection. Therefore, in the Newman projection, Br eclipses CH3, Cl eclipses H, and CH3 eclipses H. In the Newman projection, we look down the C-C bond, which is perpendicular to the image surface. The front carbon is represented by the point where the three lines meet. The back carbon is represented by the circle. Each line represents a C-X bond, where X is a substituent. Try to visualize the rotation of the molecule, with the carbon on the left coming from the screen surface towards you. Now you don\'t see the C-C bond, since it\'s perpendicular to the surface. You see only the front carbon atom (the other carbon is hidden behind it). The substituents\' bonds on the front carbon are directed towards you, and the bonds on the back carbon are directed away from you.

non-polar covalent bond

EN: 0.0-0.5

polar covalent bond

EN: 0.5-2.0

ionic bond

EN: >2.0

Under the reaction of limonen with excess Br2, what mechanism is in effect?

Electrophilic addition

The solubility data table shows that both benzoic acid and benzocaine are significantly more soluble in ethanol than they are in water. Why is ethanol not a suitable solvent for the solvent extraction of benzoic acid and benzocaine from aqueous solution?

Ethanol is miscible in water.

The solubility data table shows that both benzoic acid and benzocaine are significantly more soluble in ethanol than they are in water. Why is ethanol not a suitable solvent for the solvent extraction of benzoic acid and benzocaine from aqueous solution? Ethanol is immiscible in water, so the benzoic acid cannot move from one layer to the other. Benzocaine and benzoic acid have solubilities in ethanol that are above the useable limit for a solvent extraction. Benzoic acid and benzocaine both contain polar protic groups. Ethanol is miscible with water.

Ethanol is miscible with water.

What layer will be on top: water or ethyl acetate for a (water/ethyl acetate mixture)?

Ethyl acetate

Natural products can be extracted into organic solvent. For example, limonene can be extracted from the largely-aqueous distillate of a steam distillation of orange peel by ethyl acetate, and eugenol can be extracted from aqueous solution into dichloromethane. The diagrams below represent the separatory funnels for the two different solvent systems. Drag and drop the layers into the appropriate box.

Ethyl acetate has a density of 0.89 g/mL, while water has a density of 1.00 g/mL. Ethyl acetate will be the upper layer in the separatory funnel. Dichloromethane has a density of 1.33 g/mL, while water has a density of 1.00 g/mL. Dichloromethane will be the lower layer in the separatory funnel.

Limonene and eugenol are natural products . Drag and drop the labels that describe these two essential oils into the appropriate boxes below their structures. Not all labels will be used.

Eugenol: acetyl coenzyme A precursor, acetogenin Limonene: isopentyl diphosphate precursor, terpene

Match the proper Newman projection and conformation to these 3D molecules.

For the molecule on the left, notice that the hydrogen atoms on one carbon atom do not line up with the hydrogen atoms on the other carbon atom. This is called a staggered conformation. If we were to look at the molecule end-on, we\'d be able to see all six hydrogen atoms without any overlap. The Newman projection resembles this end-on view. For the molecule on the right, notice that the hydrogen atoms on one carbon atom line up with the hydrogen atoms on the other carbon atom. This is called an eclipsed conformation. If we were to look at the molecule end-on, we\'d see only three hydrogen atoms (because the other three are blocked from view). The Newman projection resembles this end-on view.

To get effective mixing in a separatory funnel, then combined level of liquids should not exceed:

Higher than the widest part of the separatory funnel.

An over the counter headache pill was crushed, extracted into ethanol / dichloromethane, and then analyzed by TLC on silica using ethyl acetate as an eluent. The pill was shown to contain: acetaminophen, aspirin, and ibuprofen.

Highest Rf Ibuprofen (most nonpolar) aspirin acetaminophen (most polar) Lowest Rf

What effect would each of the following changes to the conditions of a GC separation have onthe retention time of the sample? The amount of sample injected is doubled... The carrier gas flow is increased... The column temperature is decreased...

If the amount of sample injected is doubled the retention time increases If the carrier gas flow is increased than the retention time decreases If the column temperature is decreased than the retention time increases

Considering that gauche interactions and 1,3-diaxial interactions both contribute 3.8 kJ/mol to the strain energy for a conformation, calculate the total strain energy for the shown conformation of cis-1,2-dimethylcyclohexane.

In cis-1,2-dimethylcyclohexane, the methyl groups are separated by a torsion angle of 60°. The steric repulsion caused by this gauche interaction destabilizes the molecule by 3.8 kJ/mol. There are also two 1,3-diaxial interactions for an additional 7.6 kJ/mol.

Match the procedural step to its purpose by dragging each step in the written procedure for the chemically active solvent extraction of a three-component mixture composed of benzoic acid, benzocaine, and a neutral organic molecule all dissolved in dichloromethane.

In order to dissolve the emulsion that forms after acid is added to the dichloromethane mixture conatining benzocaine, one should add water. To handle the separatory funnel correctly, cradle the inverted separatory funnel in the palm of the hand and hold the stopper between the fingers of the same hand. In order to precipitate the benzocaine, one should add base to the aqueous acidic layer mixture. Place a beaker under your separatory funnel in case your stopcock leaks. This will allow you to recover your mixture and not lose any product. For a detailed safety protocol and specific directions, please consult your laboratory manual.

Translate the given theoretical conformer from the wedge-and-dash drawing into its Newman projection.

In the Newman projection, we look down the C-C bond, which is perpendicular to the image surface. The front carbon is represented by the point where the three lines meet. The back carbon is represented by the circle. Each line represents a C-X bond, where X is a substituent. The orientation of substituents in the staggered Newman projection must match that in the wedge-and-dash drawing, or else it would be a different conformer (i.e., do not rotate about the C-C bond). By inspecting the wedge-and-dash drawing, we know that Br is trans to H, OH is trans to Cl, and F is trans to SH, which means that they will be opposite to each other in the Newman projection. Since Br is shown on the front carbon, the other substituents on this carbon are F and OH. The back carbon has H, SH, and Cl substituents. Try to visualize the rotation of the molecule, with the carbon on the right coming from the screen surface towards you. Now you don\'t see the C-C bond, since it\'s perpendicular to the surface. You see only the front carbon atom (the other carbon is hidden behind it). The substituents\' bonds on the front carbon are directed towards you, and the bonds on the back carbon are directed away from you.

Isopentane (a.k.a. 2-methylbutane) is a compound containing a branched carbon chain. A Newman projection is given for six conformations about the C2-C3 bond of isopentane. On the curve of potential energy versus angle of internal rotation for isopentane, label each energy maximum and minimum with one of the conformations.

In the Newman projections, we are looking down the C2-C3 bond. C2 is in front and has two attached methyl groups; C3 is behind C2 and C3 has one attached methyl group. The angle of internal rotation (a.k.a. dihedral angle or torsion angle) indicates the degree of rotation about the C2-C3 bond (rather than rotation of the entire molecule). Because the x-axis indicates the angle of internal rotation, looking sequentially from conformation to conformation (i.e., A to B to C, etc.) should convey sequential \"snapshots\" of one full rotation - in 60° increments - about the C2-C3 axis. The set of three staggered conformations is at lower potential energy relative to the set of three eclipsed conformations because van der Waals repulsions are minimized in staggered conformations. In the staggered (low-energy) set, conformation C has the highest energy (or least low energy) because of van der Waals repulsions between the back methyl group with both front methyl groups. Staggered conformations A and E experience less van der Waals repulsions because the rear methyl interacts with only one of the front methyl groups. In the eclipsed (high-energy) set, conformation F has the lowest energy (or least high energy) because each methyl group is aligned with a hydrogen, so van der Waals repulsions are relatively minimized. Eclipsed conformations B and D have the highest energy because they have eclipsed methyl groups.

Identify the atoms that participate in 1,3-diaxial interactions in the shown conformation of trans-1,2-dimethylcyclohexane.

In the diaxial conformer of trans-1,2-dimethylcyclohexane, the methyl groups are separated by a torsion angle of 180°. Each axial methyl group experiences a steric repulsion with two axial hydrogens on the same face. The steric repulsion caused by these four 1,3-diaxial interactions destabilizes the molecule by 4 × 0.9 kcal/mol.

Considering that gauche interactions and 1,3-diaxial interactions both contribute 3.8 kJ/mol to the strain energy for a conformation, calculate the total strain energy for the shown conformation of trans-1,2-dimethylcyclohexane. #2

In the diaxial conformer of trans-1,2-dimethylcyclohexane, the methyl groups are separated by a torsion angle of 180°. There are no gauche interactions between the methyls in the molecule shown, but there are four 1,3-diaxial interactions for a total strain energy of 15.2 kJ/mol. (4 × 3.8 kJ/mol).

Identify the gauche interactions between methyl groups in the shown conformation of trans-1,2-dimethylcyclohexane.

In the diaxial conformer of trans-1,2-dimethylcyclohexane, the methyl groups are separated by a torsion angle of 180°. There are no gauche interactions in the molecule shown.

Identify the atoms that participate in 1,3-diaxial interactions interactions in the shown conformation of trans-1,2-dimethylcyclohexane.

In the diequatorial conformer of trans-1,2-dimethylcyclohexane, the methyl groups are separated by a torsion angle of 60°. There are no 1,3-diaxial interactions in the molecule shown.

Does density always increase as molar mass increases?

No.

A prelimary investigation reveals that an unknown material has a melting range around 250 °C. The heating curves for a melting point apparatus are shown below. Use the curves to determine what voltage would be required to produce a temperature change of 2 °C/min close to the needed melting point. *image not provided of two graphs What voltage must the melting point apparatus be run at in order to produce a 2 °C/min change near 250°C? Enter the votage to the nearest 5 volts.

Note that the second graph gives the relationship between voltage and temperature for a given rate. Using the graph on the right, find 250 °C on the vertical axis then read across until you reach the second curve, ascribed to 2 °C/min, then read vertically down to find the voltage as 65 V. *answer may vary Answer: 67 Volts

The carrier gas in GC separation is usually an inert gas such as nitrogen, helium or argon, but can also be hydrogen. What are the pros and cons of using hydrogen as a carrier gas in a GC separation?

Pros: hydrogen is cheaper than helium, it can be generated in the GC instead of from gas tanks, and there is a greater difference in mass between carrier gas and sample than nitrogen Cons: explosion hazard

functional group: ester

R-(C=O)-O-R (-oate)

functional group: carboxylic acid

R-(C=O)-OH (-oic acid)

functional group: ketone

R-(C=O)-R (-one)

functional group: thioester

R-(C=O)-S-R (-thioate)

functional group: acyhalide

R-(C=O)-X

functional group: amine

R-(N-R)-R (-amine)

functional group: sulfoxide

R-(S=O)-R (sulfoxide)

functional group: nitrile

R-C≡N (-nitrile)

In regards to the E2 mechanism, rank the leaving groups in order of increasing reaction rate.

R-F, R-Cl, R-Br, R-I

functional group: alcohol

R-O-H (-ol)

functional group: ether

R-O-R (ether)

functional group: thiol

R-S-H (-thiol)

Purpose? Enough calcium chloride to cover half the bottom of the flask was added.

Remove dissolved water is from the reaction mixture.

Eugenol, the essential oil found in cloves, can be isolated by steam distillation because it is insoluble in water and has a much higher boiling point than water. Use data from the table to calculate the temperature at which a mixture of eugenol and water will boil. What temperature will a mixture of eugenol and water boil at?

Slightly less than 100 degrees C.

Eugenol, the essential oil found in cloves, can be isolated by steam distillation because it is insoluble in water and has a much higher boiling point than water. Use data from the table to calculate the temperature at which a mixture of eugenol and water will boil.

Slightly less than 100 °C.

During the recrystallization of a solid, the sample is dissolved in hot solvent then filtered while hot. The filtrate is allowed to cool and the mixture is filtered a second time. What effect will result if the filtrate solution is cooled too rapidly?

Small impure crystals will form.

The active ingredients in an over the counter analgesic pill were separated by TLC on silica, using a solvent system of hexanes and ethyl acetate. Identify where the waste generated by this process should go.

Solid Waste: TLC plate Non-Chlorinated Organic Waste: hexane, ethyl acetate, rinse acetone Broken glass: spotting capillary

The gauche conformation of butane occurs when the dihedral angle between the C1-C2 bond and the C3-C4 bond is 60°. There is steric strain in the molecule because of the proximity of the two methyl groups. Would the steric strain in this molecule increase or decrease if the C1-C2-C3 bond angle (and the C2-C3-C4 bond angle) was increased to more than 109.5° ?

Steric strain will decrease because groups are moving further apart.

The gauche conformation of butane occurs when the dihedral angle between the C1-C2 bond and the C3-C4 bond is 60°. There is steric strain in the molecule because of the proximity of the two methyl groups. Would the steric strain in this molecule increase or decrease if the C1-C2-C3 bond angle (and the C2-C3-C4 bond angle) was increased to more than 109.5° ?

Steric strain will decrease because groups are moving further apart.

The suggested procedure for spotting a sample on a TLC plate involves transferring a droplet of concentrated solution from a capillary onto the plate, allowing it to dry, then repeating the process over the existing spot. Why is it advised to spot multiple times? Select all answers that apply.

The higher compound concentration facilitates visualization. To achieve a high concentration of sample in a small spot.

A 0.7 mL mixture of pentanol and heptanol are separated and collected using preparative gas chromatography on a GC fitted with a polar column and a TCD detector. During the separation, why are the injection port and detector heater to a higher temperature than the column? -all samples leaving the column must be vaporized before leaving the GC, so the thermal conductivity detector is run at a hot temperature -a heated injector creates flash vaporization which allows separation at temperatures lower than the boiling point of the sample -the wire in the thermal conductivity detector needs to be cooled by the eluent in order to register a signal -the injector must be kept at a higher temperature than the column to allow the sample the opportunity to effectively solidify in the column

The injection port and detector are heated to a higher temperature because a heated injector creates flash vaporization which allows separation at temperatures lower than the boiling point of the sample and the wire in the thermal conductivity detector needs to be cooled by the eluent in order to register a signal

The gauche conformation of butane occurs when the dihedral angle between the C1-C2 bond and the C3-C4 bond is 60°. There is steric strain in the molecule because of the proximity of the two methyl groups. Would the magnitude of this steric strain increase or decrease if the dihedral angle was increased from 60° to 65°?

The magnitude of steric strain will decrease because the groups are moving further apart.

The gauche conformation of butane occurs when the dihedral angle between the C1-C2 bond and the C3-C4 bond is 60°. There is steric strain in the molecule because of the proximity of the two methyl groups. Would the magnitude of this steric strain increase or decrease if the dihedral angle was increased from 60° to 65°? *There is a picture but it doesn't matter because the question is not specifically asked about it.

The magnitude of the steric strain will decrease because the groups are moving further apart

How would the melting point range of a pure organic material be changed if there was a tiny shard of broken glass inside the melting point capillary?

The melting range would not be affected.

How would the melting range of a pure organic material be changed if there was a tiny shard of broken glass inside the melting point capillary?

The melting range would not be affected. (Glass is not soluble in the liquid --> will not change mp)

When comparing melting temperature ranges of pure and impure samples, which of the following statements describes the melting temperature range of an impure sample? For a pure substance,

The melting temperature range is narrower than that of an impure sample.

When comparing melting temperature ranges of pure and impure samples, which of the following statements describes the melting temperature range of an impure sample? Select all answers that apply.

The melting temperature range of an impure sample is lower than that of a pure sample. The melting temperature range of a pure sample is narrower than that of an impure sample.

In regard to the TLC plate you will be using in lab, which statement is FALSE?

The mobile phase is more polar than the stationary phase.

How are molecules ranked in terms of their carbonyl stretching frequency in the infared spectrum?

The more carbons a molecule has, the greater its carbonyl stretching frequency.

In order to perform a bromine test on a compound, it must be treated with a dilute solution of bromine. Which of the following results will indicate the presence of an alkene?

The reddish color of the bromine will disappear

During the bromine test, what result will indicate the presence of an alkene?

The reddish color of the bromine will disappear.

During the developing of a TLC plate, it is common to place a cover on the chromatography chamber and have a piece of moist filter paper line the walls of the TLC chamber. Why is the moist filter paper in the TLC chamber of importance during thin-layer chromatography?

To prevent evaporation from the TLC plate during development. To ensure that the air in the chamber is saturated with solvent vapor.

During the recrystallization of a solid, the sample is dissolved in hot solvent then filtered while hot. The filtrate is allowed to cool and the mixture is filtered a second time. What is the purpose of the initial hot vacuum filtration in the recrystallization process?

To remove insoluble solid impurities.

The gauche conformation of butane occurs when the dihedral angle between the C1-C2 bond and the C3-C4 bond is 60°. There is steric strain in the molecule because of the proximity of the two methyl groups. When you consider that E(strain) = E(stretch) E(angle) E(torsion) E(steric), would E(torsion) increase or decrease when the dihedral angle of gauche butane is increased from 60° to 65° ? *There is a picture but it doesn't matter because the question is not specifically asked about it.

Torsional strain increases(note that steric strain decreases because methyl groups move further but torsional increased because the otehr bonds in teh molecule will move closer to being eclipsed=higher energy)

The gauche conformation of butane occurs when the dihedral angle between the C1-C2 bond and the C3-C4 bond is 60°. There is steric strain in the molecule because of the proximity of the two methyl groups. When you consider that E(strain) = E(stretch) E(angle) E(torsion) E(steric), would E(torsion) increase or decrease when the dihedral angle of gauche butane is increased from 60° to 65° ?

Torsional strain increases.

The gauche conformation of butane occurs when the dihedral angle between the C1-C2 bond and the C3-C4 bond is 60°. There is steric strain in the molecule because of the proximity of the two methyl groups. When you consider that E(strain) = E(stretch) E(angle) E(torsion) E(steric), would E(torsion) increase or decrease when the dihedral angle of gauche butane is increased from 60° to 65° ?

Torsional strain increases.

What layer will be on top: water or dichloromethane for a (water/dichloromethane mixture)?

Water

What will be in the aqueous top layer in the reaction to produce allyl 2-napthyl ether?

Water, sodium 2-naptholate, sodium hydroxide, benzytributylammonium chloride.

There are four major methods of purification in the chemistry laboratory. Which of the following techniques are included in the four most common methods for separation and purification? Select all that apply.

YES- Extraction, distillation, chromotography NO- Subtraction

Which of the following are requirements for a suitable solvent when performing a recrystallization?

YES- The solvent should dissolve the compound while hot; The solvent should not chemically react with the compound NO- The solvent should dissolve the compound while cold; The solvent should chemically react with the compound

bond order equation

[(bonding e⁻) - (anti bonding e⁻)]÷2 (must be >0 for molecule to exist)

("Who Has My Compound?") Why is it good practice to perform a mixed melting point determination at two different ratios of unknown to known materials in the melting point capillary? a. Because it is possible that one particular combination of materials generates a eutectic. b. Two quantities are not needed. A 1:1 combination will suffice. c. In case one of the materials in the mixture sublimes. d. Because inconsistencies in the finely divided powder will alter the melting point.

a

(Molecular Models [Post]) Identify the atoms that participate in 1,3-diaxial interactions interactions in the shown conformation of trans-1,2-dimethylcyclohexane. EQUITORIAL. How many total 1,3-diaxial interactions are present in this molecule? a. 0 b. 1 c. 2 d. 3 e. 4

a

(Molecular Models [Post]) Identify the gauche interactions between methyl groups in the shown conformation of trans-1,2-dimethylcyclohexane. AXIAL. How many gauche interactions are there between methyl substituents in this molecule? a. 0 b. 1 c. 2 d. 3 e. 4

a

(Recrystallization of Acetanilide) When is recrystallization not a suitable method to purify an organic material? a. When the organic material is not a solid. b. When the organic material is highly impure. c. When the organic material is thermally unstable near its melting point. d. When the organic material is soluble in water.

a

A strong IR absorbance in the 1670‐1830 cm‐1 range is present in which of the following: 1. alkenes 2. esters 5. alcohols 3. aldehydes 4. carboxylic acids a. 2,3,and4 b. 2,3,and5 c. 1,4,and5 d. 2,4,and5 e. 1,2,and3

a

At the end of the phase transfer catalysis experiment, what molecule had the highest Rf value when you ran the TLC? a. ally 2‐naphthyl ether b. naphthol c. benzyltri‐n‐butylammonium chloride d. naphtholate anion e. methylene chloride

a

Compounds A, B and C are three unknown compounds. Compound A melts at 130-133°C, Compound B melts at 132-134°C and Compound C melts at 140-143°C. Compound D is a known compound who melts at 131-134°C. The mmp A+B is 131-133°C. The mmp A+C is 138-142°C. The mmp B+C is 139-144°C. The mmp A+D is 130-134°C. The mmp C+D is 134-140°C. What can you conclude about your unknowns? a. A=B=D b. B=C=D c. A=B=C d. B=C e. C=D

a

Considering thin layer chromatography, which of the following statements is correct? b. Spots are visible on a TLC plate only if the compounds fluoresce. c. A TLC jar should be washed with water prior to use. d. When spotting a TLC plate, the bigger the spot, the better. e. TLC gives Rf values between 1 and 100.

a

During the purification of allyl-2-naphthyl either in the phase transfer catalysis experiment, some products were retained the in the silica gel mini-column. What is the nature of these retained products? a. polar b. non-polar c. acidic d. basic e. none of the above

a

In attempting to recrystallize impure benzoic acid, it was found that the benzoic acid formed a layer of oil on top of the recrystallizing solvent as the solution cooled. How could this problem be solved? a. Reheat the solution to completely dissolve the oil, add a small portion of hot solvent, and allow the solution to cool slowly. b. Reheat the solution, and then quickly place the hot solution in an ice bath to induce crystallization. c. Add NaOH to make the solution basic, and then allow the solution to cool slowly. d. Add HCl to acidify the solution, and then allow the solution to cool slowly in an ice bath. e. Add an organic solvent to help dissolve the oil, reheat the solution for a few minutes, and then allow it to cool.

a

In reference to TLC, which statement best describes the change in Rf caused by a change in solvent polarity? a. Adding a polar solvent causes the Rf of the compound to increase. b. Adding a polar solvent causes the Rf of the compound to decrease. c. Adding a nonpolar solvent causes the Rf of the compound to increase. d. Adding water causes the Rf of the compound to decrease. e. Solvent polarity has no effect on the Rf of a compound.

a

The fingerprint region of the IR refers to: a. the portion of the spectrum from 1500‐400 cm‐1 that is unique for nearly every compound b. the part of the spectrum that results from someone placing a dirty finger on the salt plate c. the portion of the spectrum that results from the vibrations of functional groups within the compound (4000‐1250 cm‐1) d. the portion of the spectrum that has the least peaks e. the portion of the spectrum from 2750‐1667 cm‐1 that results from vibrations specific to aldehydes, nitriles, and alcohols

a

The reaction performed in the dehydrohalogenation experiment was an E2 reaction. Which of the following statements about E2 reactions is false? a. Carbocation intermediates are common in E2 elimination reactions. b. E2 reactions are stereospecific. c. Strong bases encourage elimination reactions. d. It is easier to perform an E2 reaction on an alkyl chloride than an alkyl fluoride. e. Tertiary alkyl halides will undergo faster elimination than secondary alkyl halides.

a

What effect on the rate of an SN1 type reaction would there be if you doubled the concentration of the nucleophile? a. it would have no effect on the rate b. stop the reaction completely c. increase the rate by a factor of 2 d. increase the rate by a factor of 4 e. decrease the rate by a factor of 2

a

What is the similarity with E2 elimination and SN2 substitution? a. Concentration of nucleophile affects the rate of the reactions b. Concentration of nucleophile does not affect the rate of the reactions c. The rate of reactivity of alkyl halides is ordered by 1 > 2 > 3 d. The rate of reactivity of alkyl halides is ordered by 3 > 2 > 1 e. Halogens are poor leaving groups for the reactions

a

When the solution is cooled very rapidly in recrystallization a. small crystals form that have a large surface area on which impurities will be adsorbed. b. the solvent may evaporate. c. some of the solvent may be left with the crystals. d. ideal recrystallization takes place. e. the impurities have less time to stick to the crystals.

a

In the phase transfer catalysis experiment, what type of analysis was used to determine the progress of the reaction? a. extraction d. distillation b. thin layer chromatography c. gas chromatography e. Recrystallization

b

Which is the correct procedure for isolating benzocaine crystals from a solution of benzoic acid and benzocaine in methylene chloride? a. Add aqueous HCl, remove aqueous layer, add NaOH to the aqueous layer, and vacuum filter the crystals. b. Add aqueous HCl, remove organic layer, add NaOH to the organic layer, and vacuum filter the crystals. c. Add aqueous NaOH, remove aqueous layer, add HCl to the aqueous layer, and vacuum filter the crystals. d. Add aqueous NaOH, remove aqueous layer and distill, place distillate in ice bath to induce crystal formation, and vacuum filter the crystals. e. Add aqueous NaOH and the phase transfer catalyst, remove aqueous layer, put in ice bath and vacuum filter the crystals.

a

Which of the following compounds would be indicated by a strong, sharp infrared absorption in the 1680-1830 cm-1 region and a strong, broad absorption in the 2500-3300 region? a. a carboxylic acid b. a ketone c. an alkene d. an amine e. an ether

a

Your experimentally determined melting point is 10 degrees low and has a 4 melting point range. This indicates that: a. your compound is impure b. you put too much material in the melting point capillary c. your compound is pure d. the Mel‐Temp thermometer is poorly calibrated e. you set the voltage on the Mel‐Temp too high

a

Lewis acid

a substance that accepts an electron pair (must have with a vacant, low-energy orbital or a polar bond to hydrogen)

Lewis base

a substance that donates an electron pair (most O and N containing compounds because of lone pairs)

("Who Has My Compound?) When comparing melting temperature ranges of pure and impure samples, which of the following statements describes the melting temperature range of an impure sample? Select all answers that apply. a. The melting temperature range of a pure sample is higher than that of an impure sample. b. The melting temperature range of a pure sample is narrower than that of an impure sample. c. The melting temperature range of an impure sample is higher than that of a pure sample. d. The melting temperature range of a pure sample is broader than that of an impure sample.

ab

classification of alkyl groups

according to the number of carbons attached to that C. -1° or primary: 1 C attached -2° or secondary: 2 C attached -3° or tertiary: 3 C attached -4° or quaternary: 4 C attached

("Who Has My Compound?") Which of the following statements about melting point determination are true? Select all that apply. a. The lower limit of the melting temperature range occurs when the first crystal starts to melt. b. The literature value of melting point is often quoted as only the lower limit. c. The melting point is a physical measure of the forces holding the material into its crystal lattice. d. The upper limit of the melting temperature range occurs when the last remaining crystal melts.

acd

During the recrystallization of an impure solid sample, the sample is dissolved in hot water then filtered while hot. The filtrate is allowed to cool and the mixture is filtered a second time. Which procedure should a student NOT do if they observe an oil forming as the solution cools?

add a small amount of ice-cold water

isotopes

atoms with the same atomic number but different mass numbers

("Who Has My Compound?") How would the melting range of a pure organic material be changed if there was a tiny shard of broken glass inside the melting point capillary? a. The melting range would increase and get broader. b. The melting range would not be affected. c. The melting range would decrease and get narrower. d. The melting range would decrease and get broader. e. The melting range would increase and get narrower.

b

(Molecular Models [Post]) Considering that gauche interactions and 1,3-diaxial interactions both contribute 3.8 kJ/mol to the strain energy for a conformation, calculate the total strain energy for the shown conformation of trans-1,2-dimethylcyclohexane. EQUITORIAL. What is the total strain energy in this molecule? a. 0 kJ/mol b. 3.8 kJ/mol c. 7.6 kJ/mol d. 11.4 kJ/mol e. 15.2 kJ/mol

b

(Molecular Models [Post]) Identify the gauche interactions between methyl groups in the shown conformation of cis-1,2-dimethylcyclohexane. How many gauche interactions are there between methyl substituents in this molecule? a. 0 b. 1 c. 2 d. 3 e. 4

b

(Molecular Models [Post]) Identify the gauche interactions between methyl groups in the shown conformation of trans-1,2-dimethylcyclohexane. EQUITORIAL. How many gauche interactions are there between methyl substituents in this molecule? a. 0 b. 1 c. 2 d. 3 e. 4

b

Compounds A and B both have melting points of 140°C. If A is mixed with B at a ratio which leads to melting at the eutectic point, the melting point of the mixture a. will remain 140°C b. will be less that 140°C c. will be greater than 140°C d. will contain two separate melting points e. cannot be determined

b

In the preparation of 3‐chloro‐3,7‐dimethyloctane, the organic layer was washed with sodium bicarbonate solution. This washing was for the purpose of: a. removing excess base b. removing the remaining acid c. drying the organic layer d. dehydration to form alkene e. increasing the solubility of the product in the organic phase

b

Retention time in gas chromatography is not affected by: a. the nature of the stationary liquid b. the concentration of the sample c. the temperature at which the column is maintained d. the rate of flow of the inert gas e. the length of the column

b

Steam distillation is used to isolate: a. salts of organic acids b. water insoluble oils c. mixtures of several volatile compounds d. better separation of two compounds with different boiling points e. low boiling products from organic reactions

b

The melting point of an impure compound is a. the same as b. lower and has a wider range c. lower and has a narrower range d. higher and has a wider range e. higher and has a narrower range (than) the corresponding pure compound.

b

The preparation of 3‐chloro‐3,7‐dimethyloctane from 3,7‐dimethyl‐3‐octanol, is an: a. SN1 reaction in which protonation is the rate determining step. b. SN1 reaction in which formation of tertiary carbocation is the rate determining slow step. c. E1 reaction in which dehydration is the rate determining step. d. SN2 reaction in which addition of chloride ion is the rate determining step. e. SN2 reaction in which dehydration is the rate determining step.

b

The raising of the oven temperature in GC will _____ the retention times of two compounds and _____ their separation. a. lengthen, decrease b. shorten, decrease c. lengthen, increase d. shorten, increase e. not effect, not effect

b

When a solution is cooled very rapidly in recrystallization: a. no crystals will form b. small crystals form that have a large surface area on which impurities will be absorbed c. ideal recrystallization takes place d. the impurities don't have time to stick to the crystals e. none of these

b

When analyzing the IR of your product from the Oxidation of a Secondary Alcohol you were looking for what in the spectra? a. The disappearance of a peak at approximately 1700 cm‐1 and appearance of broad peak at approximately 3300 cm‐1. b. The appearance of a peak at approximately 1700 cm‐1 and disappearance of broad peak at approximately 3300 cm‐1. c. The appearance of a strong peak at approximately 2200 cm‐1 and disappearance of strong peak at approximately 1700 cm‐1. d. The disappearance of a strong peak at approximately 2200 cm‐1 and appearance of strong peak at approximately 1700 cm‐1 e. None of these cases are correct; we didn't analyze the product by IR.

b

Which of the following is essential for the separation of two compounds in a mixture by preparative GC? a. They must have a different boiling point. b. They have different distribution in the stationary phase. c. They must have different molecular weight. d. Large injection volume. e. They must be volatile and thermally unstable.

b

Which of the following is one of the criteria used to determine whether compounds can be purified by gas chromatography? a. polarity b. thermal stability c. solubility d. melting point e. viscosity

b

Which of the following variations of 1,2‐dimethylcyclohexane in the chair conformation is the most stable? a. methyl groups are diaxial b. methyl groups are diequatorial c. methyl one is axial, methyl two is equatorial d. methyl one is equatorial, methyl two is axial e. all are equally stable since it is in the chair conformation

b

You are performing a solvent extraction of a neutral, basic, and an acidic compound. All are very soluble in CH2Cl2 (dichloromethane) and slightly soluble in H2O. You have added HCl to the separation funnel and shaken the funnel. The basic compound is in the ___________ layer, the acidic compound is in the ___________ layer, and the neutral component is in the ___________ layer. a. bottom, top, top b. top, bottom, bottom c. top, top, bottom d. bottom, bottom, top e. top, bottom, top

b

why do bonds form?

because energy always flows out of the system when a bond is formed (making bonds always releases energy)

benefits and pitfalls of valence bond theory

benefits -predicts bond strengths, lengths, and rigidity pitfalls -can't predict diamagnetic or paramagnetic -can't explain delocalization because assumes electrons are localized in orbitals

in bonding and anti bonding MO's where is most of the electron density?

bonding MO's: between the 2 atoms anti bonding MO's: node prevents the electrons from contributing to bonding

polar covalent bonds

bonding e⁻ are attracted more strongly by one atom than by the other (e⁻ distribution is not symmetrical)

what were the results of the bromine and potassium permanganate tests

both positive; double bonds and easily oxidizable group detected

stereochemistry

branch of chemistry concerned with the three-dimensional aspects of molecules -σ bonds are cylindrically symmetrical and can rotate

how do cyclic molecules minimize angle strain and torsional strain?

by assuming nonplanar conformations

(Molecular Models [Post]) Identify the atoms that participate in 1,3-diaxial interactions in the shown conformation of cis-1,2-dimethylcyclohexane. How many total 1,3-diaxial interactions are present in this molecule? a. 0 b. 1 c. 2 d. 3 e. 4

c

According to the Merck Index, the amount of solvent necessary to dissolve 1.0 g of m‐nitrobenzoic acid is: water ‐ 146 mL, ethanol ‐ 3 mL, chloroform ‐ 220 mL, ether ‐ 4.5 mL, acetone ‐ 2.5 mL. Why wouldn't acetone be the best solvent to extract m‐nitrobenzoic acid from water? a. The acid is not soluble enough in acetone. b. The acid is more soluble in water than in acetone. c. Acetone is soluble in water. d. 2.5 mL of acetone is not enough to do an extraction. e. Acetone has a lower density than water.

c

During the extraction lab you extracted benzocaine out of CH2Cl2. What was the reactive functional group and what reagent was used to make this happen? a. The functional group was a carboxylic acid and the reagent was a carboxylic base. b. The functional group was an alcohol and the reagent was an acid c. The functional group was an amine and the reagent was an acid d. The functional group was a carboxylic acid and the reagent was a base. e. The functional group was a amide and the reagent was an acid.

c

If you take the melting point of an impure substance, the observed melting point range will be ______ relative to the melting point range observed for the pure substance. a. higher and broader b. higher and narrower c. lower and broader d. lower and narrower e. neither higher nor lower, but broader

c

In the Who Has My Compound? experiment, how did the inorganic sand affect the melting point benzoic acid? a. increased the melting point b. decreased the melting point c. no effect on the melting point d. broadened the melting point range e. decreased the melting point range

c

In the extraction of eugenol from clove oil, the clove oil is treated with NaOH. Two layers form, an aqueous and a methylene chloride phase. Which of the following statements is true? a. The OH‐ cleaves the ether bond. The eugenol molecule will be found in the top layer. b. The OH‐ cleaves the ether bond. The eugenol molecule will be found in the bottom layer. c. The OH‐ removes the phenolic hydrogen. The eugenol salt will be found in the top layer. d. The OH‐ removes the phenolic hydrogen. The eugenol salt will be found in the bottom layer. e. The OH‐ nucleophilically adds to the double bond. The derivative will be found in the lower layer.

c

In the kinetic study of SN1 solvolysis, the nucleophile in the reaction is? a. -OH b. H3O+ c. H2O d. R+ e. There is no nucleophile in this reaction

c

Most organic compounds are less dense than water and will be on top of the aqueous phase in a separatory funnel. Which of the following organic phases breaks this rule and will be on the bottom? a. hexane b. ether c. dichloromethane d. ethyl acetate e. toluene

c

The computer calculated that the local minimum for the gauche butane conformation had a dihedral angle of: a. 0° b. 60° c. 65° d. 90° e. 180°

c

The dehydrohalogenation of 3-chloro-3,7-dimethyloctane (an E2 reaction) is favored over substitution because: a. a slightly basic nucleophile is used b. a highly polarizable nucleophile is used c. a tertiary halide is used d. a primary halide is used e. a strongly acidic nucleophile is used

c

The rate law: rate = k[RCl][‐OH] is representative of what type of kinetics? a. zero order d. third order b. first order e. fourth order c. second order

c

What is the hybridization of the oxygen in ethanol? a. sp b. sp2 c. sp3 d. s e. none of the above

c

What type of detector is used in the GC instruments used in the A&M Organic Labs? a. UV absorbance detector b. FTIR detector c. Thermal conductivity detector d. Flame ionization detector e. Ionic detector

c

Which of the following statements about steam distillation is/are true? 1. A steam bath is used as a heat source. 2. Steam distillation is only effective for compounds that are not very water soluble. 3. The boiling point of the mixture being distilled will be lower than any of the components of the mixture. a. 1, 2, and 3 b. 1 and 2 c. 2 and 3 d. 3 only e. 2 only

c

Why do you add boiling chips to a solution that will be heated? a. to keep the solution homogeneous b. to increase the rate of reflux c. to promote even boiling d. to lower the boiling point e. all of these

c

You have treated 10.0 g of 2‐methyl‐2‐butanol (MW = 88.15; density = 0.805 g/mL) with concentrated HCl and purified the product by extraction and distillation. Your product is 9.0 g of 2‐chloro‐2‐methylbutane (MW = 106.60; density = 0.865 g/mL). The percent yield is: a. 90% d. 67% b. 83% e. 60% c. 74%

c

Which of the following are commonly used oxidizing agents? Select all that apply.

chromic acid & sodium dichromate

Linear Combination of Atomic Orbitals (LCAO)

combine either constructively (bonding orbital) or destructively (anti bonding orbital)

mid 1700s

compounds obtained from plants and animals were hard to isolate and purify because they decomposed easily

alkane nomenclature: 12 C

dodecane

carboxylic acids

contain -CO₂H grouping. involved in almost all metabolic pathways, but usually exist as their anions because of the typical pH of 7.3 in cells (e.g. acetic acid, pyruvic acid, and citric acid)

hydrocarbon

contain only C and H -saturated (aliphatic): only single bonds -unsaturated: double or triple bonds

what was the objective of this lab

cyclohexanol will be dehydrated to form cyclohexene via en E1 elimination reaction

("Who Has My Compound?") Which of the following statements best describes a eutectic? a. The composition of a mixture of two components that generates the highest possible melting point. b. The composition of a mixture of two components in an exact 1:1 ratio. c. The composition of a mixture of two components that can never dissolve in one another. d. The composition of a mixture of two components that generates the lowest possible melting point.

d

(Molecular Models [Post]) Considering that gauche interactions and 1,3-diaxial interactions both contribute 3.8 kJ/mol to the strain energy for a conformation, calculate the total strain energy for the shown conformation of cis-1,2-dimethylcyclohexane. What is the total strain energy in this molecule? a. 0 kJ/mol b. 3.8 kJ/mol c. 7.6 kJ/mol d. 11.4 kJ/mol e. 15.2 kJ/mol

d

An ideal recrystallization solvent will a. dissolve lots of the compound at room temperature and little at high temperatures b. dissolve lots of the compound at room temperature and lots at high temperatures c. dissolve very little of the compound at any temperature d. dissolve little of the compound at room temperature and lots at high temperatures e. react with the compound being recrystallized

d

Eugenol and limonene: a. are an acetogenin and a terpene, respectively b. are a terpene and an acetogenin, respectively c. are natural products d. a and c e. b and c

d

In preparative gas chromatography, as the amount of sample injected increases a. the resolution increases b. the sample goes through the column faster c. the peak overlap decreases d. the peak overlap increases and becomes unacceptable e. the recovered sample purity increases

d

In preparative gas chromatography, as the amount of sample injected increases a. the resolution increases b. the sample goes through the column faster c. the peak overlap decreases d. the peak overlap increases e. the recovered sample purity increases

d

In the fractional distillation of an ideal solution of two miscible liquids, the vapor contains: a. equal amounts of each component b. only the more volatile component c. a fixed amount of the less volatile component d. more of the more volatile component e. only the less volatile component

d

In the preparation of 3-chloro-3,7-dimethyloctane, you performed a silver nitrate test on the product. Hopefully, you witnessed the immediate formation of a white precipitate. What was the precipitate? a. Ag(NO)3 b. AgNO3 c. AgBr d. AgCl e. AgI

d

The term antiperiplanar means: a. the product alkene has a dihedral angle of 180° b. the alkene distribution follows the Zaitsev rule c. the abstracted proton and the leaving group are on the same atom d. the abstracted proton and the leaving group have a dihedral angle of 180° e. the planes of the abstracted proton and the leaving group are perpendicular

d

When performing preparative gas chromatography, a. the collection tube must be capped while collecting to avoid the loss of volatile solute b. the collection tube must be capped while collecting to avoid contamination of the collected sample by impurities in the air c. the collection tube must be capped while collecting to avoid the absorption of water by the collected sample which would ruin the acquired IR spectra d. the collection tube must be uncapped to allow free passage of vapor through the tube e. during collection of a solute, the sample tube must be maintained in a downward slope to keep the GC port from plugging up

d

Which of the following is true about melting point determination? a. At the melting point of a substance, the solid and vapor states exist in equilibrium. b. An impure compound has a narrow, sharp melting point range. c. A solid is said to sublime when it first liquefies and then vaporizes to a gas. d. At the eutectic point, the melting point of a mixture of two compounds is sharp. e. Although a substance may exist in different crystalline forms, it has only one characteristic melting point.

d

Which one of the following tests cannot be used to detect the presence of eugenol? a. ferric chloride test d. silver nitrate test b. Baeyer test e. b and c c. bromine test

d

You inject a mixture of these three compounds on a non‐polar column: acetone, bp 56 C; ethyl acetate, bp 77 C; benzene, bp 80 C. Order the three compounds by increasing retention time. a. benzene, acetone, ethyl acetate b. ethyl acetate, acetone, benzene c. benzene, ethyl acetate, acetone d. acetone, ethyl acetate, benzene e. acetone, benzene, ethyl acetate

d

A Williamson ether synthesis between 2-naphthol and allyl bromide is performed in the presence of a phase transfer catalyst and strong base in dichloromethane solution. The reaction mix contains: unreacted allyl bromide, unreacted 2-naphthol, benzyltributylammonium chloride, allyl naphthyl ether, and dichloromethane. The reaction mix is passed through a silica gel mini column. What are the components of the mixture that elute from the column?

dichloromethane allyl naphthyl ether

resonance structures

differ only in the placement of the π and non bonding valence e⁻. the actual structure is an average of the multiple structures

1,3-diaxial interactions

difference between the axial and equatorial conformations is due to steric strain caused by 1,3-diaxial interactions

bond length

distance between the nuclei that leads to maximum stability (valley in graph)

saying that one particular conformation is "more stable" than another

doesn't mean it adopts and maintains only the more stable conformation because rotations around σ bonds occur rapidly, creating equilibrium between conformations (at any instant larger percentage will be found in a more stable conformation than in a less stable one

weak acids

donate a small fraction of their H's to H₂O

zwitterion form

doubly charged form (i.e. + and -), the naturally occurring state of most amino acids (-NH₂ and -CO₂H). due to amino acids having both acidic and basic sites within the same molecule (i.e. internal acid-base reaction)

(Molecular Models [Post]) Considering that gauche interactions and 1,3-diaxial interactions both contribute 3.8 kJ/mol to the strain energy for a conformation, calculate the total strain energy for the shown conformation of trans-1,2-dimethylcyclohexane. AXIAL. What is the total strain energy in this molecule? a. 0 kJ/mol b. 3.8 kJ/mol c. 7.6 kJ/mol d. 11.4 kJ/mol e. 15.2 kJ/mol

e

(Molecular Models [Post]) Identify the atoms that participate in 1,3-diaxial interactions in the shown conformation of trans-1,2-dimethylcyclohexane. AXIAL. How many total 1,3-diaxial interactions are present in this molecule? a. 0 b. 1 c. 2 d. 3 e. 4

e

An sp carbon typically has ___ atoms attached to it with bond angles of about ____. a. 3 ; 180° d. 4 ; 109° b. 4 ; 120° e. 2; 180° c. 5 ; 109°

e

Before returning your bin of glassware to the stockroom, you are required to rinse the glassware with acetone to: a. insure that all traces of water have been removed b. insure that no traces of organic soluble material has remained in the flasks c. insure that no unwanted reaction will occur the next time the glassware is used, owing to the presence of a contaminant d. aandb e. a,bandc

e

Benzoic acid and phenol can be differentiated in the infrared because benzoic acid shows an absorption near ______ and phenol does not. a. 3400 cm‐1 d. 2950 cm‐1 b. 2100 cm‐1 e. 1700 cm‐1 c. 1050 cm‐1

e

By plotting the natural logarithm (ln) of the initial concentration of alkyl halide ([RCl]0) over the concentration of alkyl halide at any time ([RCl]t) as function of time for a first order reaction, the plot will yield: a. A straight line with slope equals the initial concentration of alkyl halide ([RCl]0) b. A hyperbola with slope equals the rate constant k c. A hyperbola with slope equals initial concentration of alkyl halide ([RCl]0) d. A straight line with slope equals zero e. A Straight line with slope equals the rate constant k

e

For the selection of an appropriate solvent in thin layer chromatography one must consider: a. polarity of absorbent b. polarity of solvent c. polarity of compounds, if known d. b and c e. a, b and c

e

In "Who Has My Compound," the lab included a solubility test for the unknown compounds in sodium bicarbonate. What purification technique uses the same chemical properties as the solubility test? a. recrystallization b. gas chromatography c. distillation d. reverse phase chromatography e. base extraction

e

In the dehydrohalogenation of 3-chloro-3,7-dimethyloctane there are three positional alkene isomers produced because: a. the alkyl halide is impure b. hydrolysis, a competing reaction, is also taking place c. the initially formed product rearranges d. the ethanol used as a solvent contains a small percentage of water e. the alkyl halide contains three different types of hydrogens that can be attacked by the base

e

In the preparation of 3-chloro-3,7-dimethyloctane, 3,7-dimethyl-3-octanol is treated with concentrated HCl to give the alkyl chloride. By which of the following pathways does this reaction proceed? a. SN1 through a carbanion intermediate b. SN2 through a carbanion intermediate c. E1 through a carbocation intermediate d. SN2 through a carbocation intermediate e. SN1 through a carbocation intermediate

e

Tertiary alcohols reacting with sodium hypochlorite yield ___________. a. ketones b. carboxylic acids c. aldehydes d. amides e. none of these

e

The boiling point of a liquid is not affected by: a. hydrogen bonding b. pressure changes c. the presence of soluble impurities d. the compound's molecular weight e. the rate of heating

e

The reaction that converts 2‐heptanol to a carbonyl compound is best described as: a. a condensation d. an ammonolysis b. a reduction e. an oxidation c. a hydrolysis

e

Which of the following statements concerning GC is true? a. Injecting larger sample volumes leads to greater sensitivity (resolution). b. Preparative GC allows purification and recovery of a compound after passing it through a GC column. c. The moving phase in GC is an inert gas. d. a, b and c e. b and c

e

Which of the following statements concerning the infrared spectroscopy experiment is WRONG? a. ATR stands for "attenuated total reflectance". b. ZnSe is the most commonly used crystal for ATR. c. Normal IR spectra show absorptions around 400‐4000 cm‐1. d. Absorptions below 1500 cm‐1 are usually considered as the fingerprint region. e. A thick layer (> 10 ) of sample is required to run ATR‐IR.

e

You are given a dichloromethane solution containing compounds A, B, and C. You first extract with 3M NaOH and find that A is in the aqueous layer. Re-extraction of the organic layer with 3M HCl leaves only C in the organic layer. Of the following, compound B is probably: a. pentane b. benzoic acid c. toluene d. sodium sulfate e. benzocaine

e

in the solvolysis of an alkyl halide

each molecule that reacts will generate a molecule of acid; we are measuring the formation of acid as a way to determine the amount of alkyl halide that has reacted

cyclohexane ring-flip

interconverting of chair conformations by exchanging axial and equatorial positions (occurs ≈10⁵ times per second) -goes through twist boat and boat forms

the first step of an SN1 reaction

is the rate-determining slow step

Limonene

isopentyl diphosphate precursor Terpene

what is true of the conformational situation for larger alkanes?

it's more complex because not all staggered and eclipsed conformations have the same energy

what is the slope of a first order reaction

k=slope; positive, linear line

rate law

kinetic order that reaction follows

cyclobutane

less angle strain than cyclopropane, but more torsional strain because of the larger number of H -slightly bent out of plane (≈25°) -110 kJ/mol

butane anti conformation

lowest energy conformation in butane where the two methyl group are 180° away from each other

What volume of eugenol will be present in 30 mL of distillate? The essential oil found in cloves, eugenol, can be isolated by steam distillation because it is insoluble in water and has a measurable vapor pressure at 100 °C even though it has a much higher boiling point than water. Use data from the table to calculate the volume of eugenol in 30 mL of distillate. Molar Mass H2O: 18 g/mol Molar Mass of Eugenol: 164 g/mol Boiling point of H2O: 100 degrees C Boiling point of Eugenol: 254 degrees C Vapor Pressure at 100 degrees C: 760 mmHg Vapor Pressure at 100 degrees C: 4.0 mmHg Density of water: 1.0 g/mL Density of Eugenol: 1.05 g/mL

mH20: 0.9947 * 18 = 17.9046 / 1 g/mL = 17.9046 morg: 0.0053 * 164 = 0.8692/ 1.05 g/mL = 0.8278 V% = Vorg/(Vorg + VH2O) * 100 (0.8278/18.7324) * 100 = 4.419% 0.04419 x 30mL= 1.3257 round to 1.33mL

Molecular Orbital (MO) Theory

mathematical combination of atomic orbitals on different atoms to form molecular orbitals

dipole moment (µ)

means of quantifying molecular polarity (µ=Q∙r) (Q=1.60∙10⁻¹⁹ C; r=distance). measured in debyes (D)

glass waste

melting point capillary

What happens in the slow step?

polar solvent aids in the dissociation of the alkyl chloride

which solvents allow for the fastest Sn1 reaction

polar; fastest in water and formic acid, slowest in acetic acid

first order reaction

rate varies only with change in the concentration of the alkyl halide

alkyl groups

remove one H from an alkane (the -ane ending replaced with -yl ending). not stable compounds themselves, they are simply parts of the larger compound

if you spill dehydrating acid what should you treat it with

sodium bicarbonate

if you spill bromine what should you treat it with

sodium thiosulfate

SN1

solvent is the nucleophile, water

A TLC plate was run in 1:1, hexane:ethyl acetate, but when developed the plate only showed baseline spots. What change could be made to get the spot(s) to move further up the plate?

spot a new plate and run in 1:4, hexane:ethyl acetate

conformations of disubstituted cyclohexanes

steric effects of both substituents must be taken into account in both chair conformations

flag-pole interaction

steric interaction in the boat form of cyclohexane

smaller Ka

stronger acid

There are four major methods of purification in the chemistry laboratory. Which of the following techniques is not included in the four most common methods for separation and purification?

sublimation

1-chloro-1-phenylethane undergoes SN1 mechanism to make 1-phenylethanol. Which of the following statements are true?

the reaction can be followed acid is produced as a product; the reaction follows first order kinetics because there is only one reactant in the RDS; the rate of gain of acid is equal to the loss of alkyl halide; the color of the BB changes from blue to yellow as it becomes more acidic

vitalism

thought that organic compounds must contain some "vital force" because they were from living sources (assumed these couldn't be made in the lab)

what are the units of k

time inverse

Why is the detector fitted to the prep GC is a TCD not an FID

to avoid the loss of sample

What is the objective of this lab?

to determine the kinetics of a solvolysis reaction and observe how a change in solvent polarity affects the rate

why do we need to keep the temperature below 90 degrees

to prevent cyclohexanol water azeotrope from forming; dont want cyclohexanol in the product

Natural products can be extracted into organic solvent. For example, limonene can be extracted from the largely-aqueous distillate of a steam distillation of orange peel by ethyl acetate, and eugenol can be extracted from aqueous solution into dichloromethane. In the two solvent systems of water/ethyl acetate and water/dichloromethane, which are the top and which are the bottom layers?

water/ethyl acetate: top = ethyl acetate; bottom = water water/dichloromethane: top = water; bottom = dichloromethane

atomic mass

weighed average mass in atomic mass units (amu) of an element's naturally occurring isotopes

to determine the rate of a chemical reaction

you must be able to measure the concentration over time

calculating % equatorial and axial in mono substituted cyclohexanes

ΔG=-RTln(Keq) -given ΔG and find Keq -equilibrium lies to the [equatorial] -therefore, Keq = [equatorial]/[axial] -make sure to add both together