orgo quiz 2

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water solubility

- Ionic - Organic ions of < 7-8 carbons - Small polar molecules - Organic compounds with one H-bond donor per 3-4 carbons

functional group region

4000-1450 in IR

b

A student carried out a simple distillation on a compound known to boil at 124 oC and they reported a boiling point of 116-117 o Analysis of the compound showed it was pure and calibration of the thermometer indicated that it was accurate. What procedural error might the student have made in setting up the distillation? a. Not insulating the distillation head with glass wool and aluminum foil b. The thermometer was placed too high in the distillation head c. Not adding anti-foaming agent d. Heating up the distillation too fast e. Not adding a boiling stone

impurities were left in the sample. the product could be contaminated or the student may have used tap water instead of distilled

A student recrystallized some impure benzoic acid and isolated it by filtration. He scraped the purified benzoic acid off the filter paper after it had dried and took the melting point as a test for purity. He was surprised that most of the white solid melted sharply between 121 and 122°C but that a small amount remained unmelted even at temperatures above 200°C. Explain this behavior.

his

Amino acids alanine (Ala), proline (Pro), cysteine (Cys) and histidine (His) are separated using TLC. Based on the Rf values provided, which amino acid has the highest affinity for the stationary phase? Ala = 0.34 Pro = 0.50 Cys = 0.82 His = 0.13

a

Based on the literature values of caffeine, why characterizing caffeine using melting point is not viable? (caffeine b.p. 170oC, m.p. 238oC) a. its vapor pressure as a solid exceeds the atmospheric temperature and sublimates b. Caffeine decomposes at its melting point c. We are recovering so little than running a melting point will be impossible

true

Because there is not an exact temperature to describe it melting point is more correctly called melting range (t/f)

c, e

Before extracting the caffeine with methylene chloride, you added Na2CO3 to the aqueous portion. What two things does the addition of base do to aid the extraction of caffeine? [check all that apply] 1. The base converts the tannins into their sodium salts, making them more soluble in water. 2. The base converts the tannins into their sodium salts, making them less soluble in water. 3. It deprotonates caffeine making them more soluble in water. 4. It deprotonates caffeine making them more soluble in dichloromethane. 5. It protonates caffeine making them more soluble in dichloromethane. 6. It protonates caffeine making them more soluble in water. a. It deprotonates caffeine making it more soluble in water. b. The base converts the tannins into their sodium salts, making them less soluble in water. c. The base converts the tannins into their sodium salts, making them more soluble in water. d. It protonates caffeine making it more soluble in dichloromethane. e. It deprotonates caffeine making it more soluble in dichloromethane. f. It protonates caffeine making it more soluble in water.

e and f

Before extracting the caffeine with methylene chloride, you added Na2CO3 to the aqueous portion. What two things does the addition of base do to aid the extraction of caffeine? [check all that apply] a. The base converts the tannins into their sodium salts, making them less soluble in water. b. It deprotonates caffeine making it more soluble in water. c. It protonates caffeine making it more soluble in water. d. It protonates caffeine making it more soluble in dichloromethane. e. It deprotonates caffeine making it more soluble in dichloromethane. f. The base converts the tannins into their sodium salts, making them more soluble in water

anti foaming agent

Chemical additive that reduces and hinders the formation of foam in liquids.

no. it is a salt and has a low ph

Could you use 1.0 M NaBr (sodium bromide) as your base in place of 1.0 M NaOH for your extractions? Why or why not? Briefly explain.

immiscible part of solvents, good solubility of target compound, poor solubility of impurities, volatility of extraction solvent, toxicity and safe properties of extraction solvent

Describe desirable properties of extraction solvents for liquid-liquid and liquid/solid extractions.

tlc carried out against gravity, cc run under gravity, tlc requires less time to separate, tlc needs more polar solvent

Difference between TLC and Column Chromatography

false

Every time the compound is contaminated the melting range will go up. (t/f)

caffeine is an organic compound and dcm is an organic solvent and like dissolves like

Explain why caffeine migrates to methylene chloride from aqueous phase during the liquid-liquid extraction.

dcm. it is insoluble in water also and has a greater density than water so will be on the bottom

If you ran out of diethyl ether, provide another suitable solvent that you could use for your extraction. Would the solvent you chose be a layer on top or bottom of the water?

no bc a drying agent can't have water and sodium sulfate pentahydrate contains 5 molecules of water

In the experiment you also used Sodium sulfate anhydrous. If you find that you have ran out of it, Could you use Sodium Sulfate pentahydrate instead? Why, or why not?

retention factor

It is a measurement of how high the compound traveled on a TLC plate and it is compared to the solvent front line

partition coefficient

It is a measurement of the solubility of a compound on the organic solvent and the aqueous solvent, it is specific for a particular compound and solvent

a

Nail polish remover is a common organic solvent mixture used by every day individuals, and these solvents are responsible for the strong odor of nail polishes. Nail polish remover is made up primarily composed of the following organic solvents: Acetone (bp = 56oC) Ethyl Acetate (bp = 77oC) Butyl Acetate (bp = 126oC) Identify the false statement below regarding this solvent mixture. a. Butyl acetate has the highest vapor pressure. b. If a bottle of nail polish is opened, acetone is the solvent you would smell most or first. c. If a bottle of nail polish remover was left open, butyl acetate would be the component most likely left in the bottle. d. In order to separate tese three components, you would need to use fractional distillation.

theoretical plate

One cycle of evaporation and condensation in a distillation.

c

Over 200 species of plants produce linalool, a terpene alcohol found in many flowers and spice plants. Linalool has multiple commercial applications, the majority of which are based on its pleasant scent (floral, with a touch of spiciness). At 20oC, 0.16 g of linalool acid dissolves in 100 ml of water, but 2.10 g of linalool dissolves in 100 ml of diethyl ether. What is the partition coefficient for linalool? a. 0.076 b. 2.1 c. 13.1 d. 42.1 e. 0.76

stationary phase

Phase that holds the compounds and whose interactions are interfered by the polar solvents

boiling chip

Small, irregularly shaped pieces of material (often made from such as alumina, calcium carbonate, porcelain or carbon) added to liquids to make them boil more smoothly.

vapor pressure

The pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature

evaporation

The process by which a liquid is converted into a vapor using latent (ambient) heat

boiling

The process where an external heating source is applied until the vapor pressure equals atmospheric pressure.

water

The solubility of a compound is 59 g per 100 mL in boiling methanol and 30 g per 100 mL cold methanol. It's solubility in water is 7.2 g per 100 mL at 95 oC and 0.22 g per 100 mL at 2 oC. Which solvent would be better for recrystallization? water or methanol

a

Two samples have the exact same melting points. Are they the same compound? What procedure could you perform to confirm this? a. Perform a "mixed" melting point = independently add each compound to a small amount of your sample and see if the melting point decreases. b. Slowly run two very precise melting points. c. Run a quick melting point for an approximate melting range, then a slow precise one. d. Run a very precise melting point and then run a fast one to double check your work.

london forces, dipole dipole

What are the intermolecular forces exhibited by caffeine?

3 15ml extractions

What is better, one 45 mL extraction, or three 15 mL extractions?

c

What is the purpose of adding Brine during an extraction? a. the presence of salt in the water layer decreases the solubility of the organic compound in the organic layer. b. the presence of salt in the water layer increases the solubility of the organic compound in the aqueous layer. c. the presence of salt in the water layer decreases the solubility of the organic compound in the aqueous layer.

a, b, c, d, e

What make a good extraction solvent? a. easily separate from compound after separation b. not react with the compounds c. exhibit high solubility for solute d. exhibit low solubility for unwanted compounds/impurities e. Be (almost) immiscible with other the solvent used f. be highly flammable

dcm has a low boiling point and if it't not cooled the dcm will begin to evaporate and the extraction won't be complete. some caffeine will be lost in the water

Why does the tea need to be cooled to room temperature before methylene chloride was added?

b

Why is it helpful to add sodium chloride added before extraction the aqueous layer with DCM? a. To make the sodium salt of caffeine and make it more soluble in water. b. To increase the dielectric constant of the water and make the caffeine choose DCM more readily. c. To help attract the caffeine into the water layer. d. To make the water more dense and become the bottom layer in the separation.

methanol is soluble in water so separation won't occur

Why is methylene chloride used for the extraction rather than methanol?

c

You prepare to perform a fractional distillation by packing a 10 cm fractionating column with glass beads. Which amount of glass beads will provide you the best separation during your fractional distillation? a. 50 mL glass beads b. 100 mL glass beads c. 200 mL glass beads d. 150 mL glass beads

fluorenone from fluorene

_______ was synthesized from _______ by air oxidation

flash point

________ for a flammable liquid is the min temp at which there are enough vapors of the liquid to ignite when an ignition source is brought near to it

hexane and toluene bc they have the largest diff in bp. fractional would be best bc its best when separating liquids of close bp

a mixture contains two of the following: hexane (bp=69), benzene (bp=80), 2-butanol (bp=99), and toluene (bp=110) which mixture of 2 compounds above will give the best possible separation between the 2 using distillation techniques. would you use simple or fractional distillation?

mobile phase

a pure solvent or a mixture of solvents

sublimation

a purification technique that involves a phase change (solid to vapor) allows the pure compound to be removed from impurities to produce a crystalline product. can be done under vacuum or at room temp

partially volatile, not react with compound being purified, have bp below mp of compound being purified

a suitable recrystallization solvent should be

the purification did not work completely. the anthranene is impure. impurities lower the melting point of a solid

after performing extraction, you take the melting point of your purified anthracene. the literature melting point of anthracene is 210-212 but you determine the melting point to be 196-2015. explain why youre melting point is low and what it means about your purification technique

na2so4

after you separate an organic phase from the water later, you might add a drying agent. what is a common drying agent

mobile phase

an eluting solvent that travels up tlc plate by capillary action

odd number

atoms that are affected by nmr must have an _______ of proton or neutron

1450-400

bending frequencies

simple distillation

benzene (80oC) from sodium hydride (solid, mp 800oC)

ir energy is absorbed by bonds when the energy of that bond is met. if that energy is met it shows up as an absorption in the spectrum. all wavelengths that don't match a bond energy transmit

briefly explain what occurs when ir energy interacts with a molecule. how is a spectrum achieved

aqueous phase

by deprotonating an acid it solubilizes in the ________

observe tlc

by eye if they are colored, or by the use of uv light, i2 stain, br2 stain (rarely), or other chemical stains that adhere to the compounds

organic phase

by protonating an acid or making a base neutral it will solubilize in the _______

aqueous phase

by protonating an amine (base) it solubilizes in the _______

steam distillation

cinnamaldehyde (bp 248 oC) from cinnamon

upside down tlc

column chromatography is

vapor pressure is the pressure above a liquid due to that liquid in the gas phase. higher vp=lower bp. hexane has the highest vp

describe what vapor pressure is and how it relates to a compounds boiling point. which compound hexane (bp=69), benzene (bp=80), 2-butanol (bp=99), and toluene (bp=110) has the highest vapor pressure

identification and purification

distillation is used for ___________

steam distillation

distillation of a liquid in a current of steam, used especially to purify liquids that are not very volatile and are immiscible with water. used for temp sensitive materials that tend to decompose at higher sustained temps

lower bp

does a lower or higher bp have a higher vapor pressure

decrease

does bp increase or decrease at higher altitudes

salting out

done by adding brine to the aqueous layer, it decreases the solubility of the organic compound in the aqueous phase allowing more of the organic compound to be transferred from the aqueous phase to the organic phase

when a mixture boils the vapor will be enriched in the compound with the lower boiling point, if the vapor condenses and evaporates again the vapor will be further enriched. each time this cycle continues the vapor becomes more pure in the lower boiling compound. a fractional distillation provides a larger surface area in which more of the cycles can take place allowing the vapor to become more pure each time

explain how fractional distillation column provides better separation what simple distillation

rapid cooling causes compound to precipitate out quickly trapping impurities in the crystals

explain why cooling the solution too quickly by immediately moving it from the hotplate to the icebath is a problem in recrystalization

more of your compound remains dissolved after recrystallization reducing your yield

explain why using a much larger volume of solvent than needed is a problem in recrystallization

sublimination

fast and easy way to purify several solids including caffeine

tlc

fast and efficient for the separation of small amounts of material and can be used to check the purity of lab samples, compare compounds for identity, follow the course of a reaction, separation, purification, etc

emulsion

formed in an extraction. a suspension of insoluble droplets of one liquid in another liquid. when formed the entire mixture has a milky appearance. disappears when allowed to sit for a few minutes

greater than 30-40

fractional distillation separates two components when bp is

by calculating the rf value and looking at the color characteristics

how can tlc be used to identify a compound

when the spot of the limiting reagent disappears

how to know when a reaction is complete on a tlc plate

gentle mixing

how to prevent emulsions

lower

impure solids generally melt at (higher, lower, the same) temp as a pure solid

ir radiation contains enough energy to stretch covalent bonds in organic molecules. the energy absorbed is particular to a given functional group.

in a couple sentences explain how the infrared energy is elated to the spectrum you observe. that is, what is going on when infrared energy in interacting with a molecule

polar compounds stick or adhere to the stationary phase through hydrogen bonding or less strongly through dipole-dipole interactions. chromatography allows you to employ increasingly more polar solvents until you entice the polar molecules

in all types of chromatography, compounds equilibrate between the mobile phase and a stationary phase. how does this allow for compounds to be separated? organic compounds adsorb to the stationary phase through intermolecular forces. what are the different types of intermolecular forces? what is the relative order of their strength

water

in an extraction involveing dichloromethane and water, which phase will be on top

more dense

in an extraction, what layer is always on the bottom

elution solvent

in liquid chromatography the mobile phase is

solid adsorbent with a liquid coating packed into a column

in liquid chromatography the stationary phase is

flammability, toxicity, expense

in selecting a good recrystallization solvent, one should also consider

2-3 seconds

in the distillation lab we wanted a drop every _______ seconds

it tells you the temperature of the vapor not the temperature of the boiling liquid

in the distillation lab what does the temperature you read on the thermometer tell you about the identity of the solvent

Infrared Spectroscopy

indicates functional groups present

molecular vibrations

infrared radiation is largely thermal energy. it induces stronger _______ in covalent bonds, which can be viewed as springs holding together two masses, or atoms

tlc

involved separation involving differential partitioning between a mobile and stationary phase

nmr

involves the study of the interaction between electromagnetic radion and the nuclei of atoms

dichloromethane

is caffeine more soluble in water or dcm

partition coefficient

k, Any organic compound with K>1.5 can be separated from water by an organic solvent. K = C1/C2 C1 = solubility of your compound in organic solvent C2 = solubility in water (aqueous) Notice that this value is independent of volume

fingerprint region

less than 1450 in IR

distillation

liquids are purified by

checking for purity, comparing 2 compounds for identity

list 2 uses for tlc

add a salt like nacl to the aqueous layer

list one way to prevent/remedy emulsions during an extraction

wear goggles, no eating drinking or chewing gum, wear gloves and remove when leaving lab

list three safety regulations that you must follow while in lab

hot filtration and recrystallization

mixture is heated up, when the compound is still soluble in the hot solvent the impurities are not and are then filtered out, filtrate is cooled down for the target compound to crystalize

low boiling points

most organic solvents used for extractions have _____ and may boil if added to a warm aqueous solution

nmr

most powerful and broadly applicable technique for structure determination

nmr

most powerful and broadly applicable technique for structure determination • Involves the study of the interaction between electromagnetic radiation (radio wave) and the nuclei of atoms • Atoms that are affected by NMR must have an odd number of proton (p+) or neutron (n).

toluene

naphthalene has a kD of 7.3 when extracting into toluene and a kD of 3.4 when extracting into hexanes. which solvent would you for extraction to reclaim the most of the compound

sources of confusion and common pitfalls in tlc

non horizontal bands (co-elute), channeling, loading sample too vigourously, column dry, crack

fractional distillation

pentane (36oC) and 2-propanol (83oC)

simple distillation

pentane (36oC) and toluene (110-111oC)

mobile phase

phase that pushes the compound up the silica gel on a tlc plate or down a column chromatography

vapor pressure

pressure of compound above its liquid or solid at a certain temp in a closed system

1. you may get sample or your hands contaminated 2. hand lotion can contaminate ir 3. you can get sick due to contamination by eating after

provide 3 viable reasons why you would need to wear gloves while using salt plates and taking an IR

mass spectroscopy

provides accurate molecular weight, gives fragmentation patterns to help piece molecule back together

c-o, c-s, c-se

put the following bonds in order from highest to lowest stretching frequencies

1. choose solvent 2. dissolve solute in hot solvent 3. cool solution to room temp slowly 4. collect crystals by filtration 5. wash crystals with cold solvent 6. dry crystals

recrystallization steps

chromatography

set of lab techniques for the separation of mixtures based on affinities

uv/visible spectroscopy

shows electronic transitions between orbitals

greater than 60-70

simple distillation separates two components when bp is

recrystallization

solids are purified by

4000-1450

stretching frequencies

partition coefficient

subtle differences in a compounds ____________ result in differential retention on the stationary phase, allowing the separation to be effective

mixed solvent recrystallization

target molecule is more soluble in one of the two solvents used, could be done modifying temps or not

nuclear magnetic resonance

tells environments and types of protons and carbons

more tightly

the ______ a compound binds to the stationary adsorbent the more slowly it moves on the tlc plate

distillation

the action of purifying a liquid by a process of heating and cooling.

polarities of the compounds in the mixture being separated

the appropriate composition of the mobile phase depends on ________

room temp

the aqueous solution needs to be at ______ before adding the organic extraction solvent

nacl

the clear disks used in sampling as thin films for ir spectroscopy are made of what materia

mobile phase, stationary phase

the mixture is dissolved in a fluid called the ____________ which carries it through the structure holding another material called the __________________

affect rf value

the solid adsorbant (silica gel vs alumina) the polarity of the compounds, the polarity of the solvent used

extract

the solution of the dissolved compounds in an extraction

immiscible

the solvent that is used for an extraction must be ________ with the other liquid

differential partitioning

the success of separation is based on ________________ between the mobile and stationary phase

their salts by adding sodium carbonate

the tannins in caffeine that are slightly soluble in dichloromethane can be eliminated by converting it to _______________

recrystallization from one solvent

the target compound should have high solubility at high temperatures. the impurity should have high solubility at low temps and either high or low solubility at high temps -hot filtration -cold filtration

extraction

the technique used to separate an organic compound from a mixture of compounds

boiling point

the temp at which the vapor pressure=external pressure (at 1 atm or 760 torr)

liquid compounds

tlc doesnt work well for ________ bc their volatility can lead to loss of the sample by evaporation

stationary phase

tlc plate made of a polar media, a thin layer of a polar solid such as silica gel or alumina, contains polar sites on the surface that adsorbs polar molecules by dipole-dipole and h-bonding interactions, is coated on an inert surface of a supporting material (glass, plastic, aluminum)

2x50 mL

to extract an organic material from an aqueous solution, would it be better to do one extraction with 100 mL ether or 2 extractions with 50 mL each of ehter

extraction

to pull out a compound from one layer into another

immiscible liquids

two liquids which are not soluble. when mixed they separate into two layers

column chromatography

upside down tlc, separates compounds in a larger scales, components: stationary phase (silica gel, alumina), mobile phase (mixed solvent, gradient elution)

melting point behavior

used to characterize purity and identity of solids by their mp range, a useful method for identification. Impure solids show a broadened (range widened) mp range and/or mp is depressed from expected literature mp.

stationary phase

usually polar-silica gel is most widely used

silica gel-sio2, alumina-al2o2

what are the two common stationary chromatography phases for tlc or column chromatography. what bonds are found in each respective stationary phase

density of solvent, temp of extraction mixture, preventing emulsions

what are things that need to be taken into account while carrying out an extraction

involves magnets

what does magnetic mean in nmr

nuclear magnetic reasonance

what does nmr stand for

in the nucleus

what does nuclear mean in nmr

uses radio frequency

what does resonance mean in nmr

molecular weight, surface area, increased polarity, stronger imf

what increases boiling point

that the dipole moment must change for the molecule

what is the one requirement for a bond stretch to show up in the ir

to separate bulk compound from eachother

what is the purpose of column chromatography

to remove trace h2o, when clumping stops or you get a snow globe effect

what is the purpose of the drying step and how do you know that you have added enough

sodium bicarbonate can neutralize both acids and bases that are still present. the gas building up is co2 as a byproduct

what is the purpose of using sodium bicarbonate in a workup extraction? what is the gas building up in your separatory funnel?

prevents pressure buildup and loss of solution

what is the reason for venting the separatory funnel in an extraction

heat the solution to remove excess solvent

what is the remedy if too much solvent is used in the recyrstallization process and no material crystallizes

characterization

what kind of technique is IR

separation

what kind of technique is extraction

purification

what kind of technique is recrystallization

purification

what kind of technique is sublimation

separation

what kind of technique is tlc

separatory funnel

what piece of specialized glassware is used in the lab to perform liquid-liquid extractions

Dichloromethane

what solvent was often used as an organic solvent in extractions

fractional, many vaporization condensation cycles take place and can efficiently separate components. more cycles helps make it more pure

what type of distillation is more efficient in the purification or separation of the two solvents

column chromatography

what was used to separate fluorenone and fluorene

higher

when distilling an ideal binary mixture of liquids through an efficient column the pot temp will be (higher, lower) than the head temp

nonpolar substances

when silica gel is the stationary phase the developing solvent moves ________ up the plate most rapidly

vent extraction mixture immediately

when using sodium carbonate or bicarbonate to extract or wash acidic contaminants from an organic solution __________ after the first inversion and subsequently after every 3-4 inversions

1665-2000

where is aromatic overtones in an arene

3200-3600 (broad)

where is the alcohol peak in an IR

2700

where is the aldehydic c-h in an aldehyde (there's 2 humps)

2100

where is the c-c triple bond in an alkyne

3000

where is the c-h bond in a nitrile

1100

where is the c-n bond in a primary amine

2200

where is the c-n triple bond in a nitrile

1600

where is the c=c in an alkene

1600

where is the c=c in an arene

1700

where is the c=o carbonyl in a IR

3300

where is the n-h bond in a primary amine (theres two humps)

3300

where is the n-h bond in a secondary amide (there's one and its longer)

3300

where is the n-h bond in a secondary amine (there's only one of them)

3300

where is the n-h in a primary amide (there's two and theyre longer)

at lower pressure the bp of liquid decreases. this is bc a liquid boils onces its vapor pressure=atmospheric pressure

while distilling 50 mL of aniline which you prepared in the lab, you record a bp of 184. the temp remains at this value throughout most of the distillation. however you talked to your friend who attends a university in denver colorado who performed the same experiment with a bp of 180. explain

carboxylic acid

wide oh peak mixed with sp3 c-h bond

polar solvents

will compete for polar sites on the adsorbent and cause faster migration of compounds up the plate

1. dissolve compounds in ether 2. extract aqueous with hcl-removes amino 3. extract aqueous with naoh-removes 2 napthoic 4. dry ether with na2so4 5. filter or decant 6. rotovap off ether

you are given a mixture containing 3 solids: anthracene, 2-napthoic acid, and 1-aminoaphthalene. describe procedure for getting pure solid anthracene by using extraction

melting point

you will collect a ________ to verify its purity and identity

extraction

• Topulloutacompound from one layer into another • Acompoundpartitions more toward where it is more soluble (equilibrium) • Partitioncoefficient • Multipleextractionsmay be needed to completely extract a substance


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