CHM2211L Exam

If a reagent happens to accidentally get into your eyes, you should stand under the safety shower in the laboratory to rinse your eyes thoroughly for at least 15 minutes.

False

T or F: Returning excess chemicals back to the bottles from which they were extracted is okay.

False

cross-linked polymer

long chains, either branched or linear, that can form covalent bonds between the polymer molecules

How do electron withdrawing groups direct incoming groups?

meta positions

How can p-phenetidine be transformed into Acetophenetidin?

Amide Synthesis

Percent Yield

(actual/theoretical) x 100

Kd

(g compound/mL organic solvent)/(g compound/mL water)

How do you calculate nominal mass?

- By adding up the atomic masses (simplified to integers) of elements in formula Ex: C21H28O2 21 x 12 = 252 28 x 1 = 28 2 x 16 = 32 Nominal Mass = 252 + 28 + 32 = 312

Explain the purpose of the hot gravity filtration. Why is it good to use the stemless funnel for this technique?

- Hot gravity filtration remove any insoluble impurities that do not dissolve when the solution is brought to its boiling point. - it is good to use the stemless funnel for this technique because this would minimize any contact between the hot solution and the funnel (crystals would block up funnel with stem)

Bilirubin:E/Z Case Study

- yellow-orange compound that forms when hemoglobin decomposes in the body - (E= "epposite") the higher priority groups are on opposite sides of the double bond. - (Z= "zee zame zide") the higher priority groups are on the same side of the double bond

What phytonutrients are found in spinach?

-Chlorophyl a -Chlorophyl b -B-carotene -xanthophylls

Considering the directing effects of the substituents on salicylamide and predict the possible structures of the iodination products. Which do you think will be the major product?

-OH is an EDG, the substituent would be directed to its para and ortho position. -NH2 is an EWG and would direct the substituent to its meta position -I think the iodine will add para to the -OH group would because the iodine group is being placed farther away from both functional groups which reduces the strain.

You have a mystery powder that could be aspirin and a pure vial of aspirin. To decide if it is pure aspirin first pack a capillary tube with pure aspirin and take its melting point. Then, pack a capillary tube with ______ and record its melting point. The mystery powder is aspirin if the melting point values of the two samples are ________.

-a mixture of pure aspirin and the mystery powder -identical

What two steps make up an electrophilic aromatic substitution?

1) aromatic ring acts as nucleophile and attacks electrophile 2) loss of proton regenerates aromatic ring

What do you look for in a recrystallization solvent?

1) completely dissolves both the desired compound and impurities at hot temperatures 2) at cold temperatures you want the desired compound to be insoluble and the impurities to remain soluble

What are the two different polymerizations examined in the making polymers experiment

1) condensation polymerization (Nylon) 2) cross-linked polymerization (Slime)

Errors of taking melting points:

1) improper amount of sample in capillary tube 2) mistaking sagging or shrinking sample as melting 3) presence of solvent causes crystals to "sweat"

A student did an experiment to determine Kd for an organic compound. They put 2.54 g of the compound in a separators funnel, then added 32.2 mL of water and 29.6 mL of ether. After thoroughly mixing everything, they separated the two layers and isolated 1.63 g of compound from the ether. Calculate Kd.

1.95

An unknown compound was determined to be 74.97% C, 8.39% H, and no nitrogen. What is the empirical formula?

100 - 74.97 - 8.39 = 16.64% O # of C: 74.97 / 12 = 6.25 # of H: 8.39 / 1 = 8.39 # of O: 16.64 / 16 = 1.04 Divide all by 1.04 (# of O) to get C:H:O 6.25 / 1.04 = 6 8.39 / 1.04 = 8 1.04 / 1.04 = 1 Empirical Formula = C6H8O

What is the perfect composition of the eluent for the spinach lab?

50:50 hexane/ethyl acetate

Why is acetone used in chlorophyll extraction?

Acetone breaks down chlorophyll's lipid bonds to a plant's thylakoid structure and suspends the pigment in solution.

Why do we have to cover the test tube of acetone and spinach mixture with parafilm?

Acetone evaporates extremely quickly when interacting with air and all the solution would evaporate

In our EAS iodination what are we adding iodine onto? What does this make?

Adding iodine to salicylamide to make iodosalicylamide

Which pigment is the least polar which is the most?

B-carotene is the least polar and chlorophyll b is the most polar

Hall of Fame or Shame Case Study

Barry bonds was rejected from hall of fame because he was accused (after BALCO received syringe) of using anabolic steroids (THG) to enhance his athletic performance. Abbreviations: -Liquid chromatography/ mass spectrometry -Gas Chromatography High Resolution Spectrometry Synthesis of THG = hydrogenation of gestrinone (alkyne to alkane) Steroid = 3, 6 carbon rings and 1, 5 carbon ring

Most organic polymers are names based on the monomers used in their production. However, poly (vinyl alcohol) is not made from vinyl alcohol, but instead from vinyl acetate that is hydrolyzed after formation of the polymer. What can't we use vinyl alcohol in this polymerization?

Because it is too unstable

IHD

C+ [(N-(H+X))/2] +1

Why is _______ used as a solvent for solid-liquid extractions?

CO2 It offers a greener alternative to other solvents, it is readily available, nonflammable, nontoxic, and safe for the environment. Ease of removal of solvent at the end of procedure, and it is relatively quick.

Do you expect chlorophyll a or chlorophyll b to be more polar? Why?

Chlorophyll b is more polar because it has the additional aldehyde group

What do all dyes have in common?

Dye molecules are chromophores!

_______ allows the dye to interact with various wavelengths of light.

EDG or EWG that add extended conjugation to the molecule

What is extraction? What types are there?

Extraction is a technique that chemists use to remove selected components from a mixture. The different types are solid-liquid extraction and liquid-liquid extraction.

What is the difference between "extracting" and "washing"?

Extraction removes desired compounds/solutions from a mixture whereas washing filters out the impurities from the desired solution. Keep extraction and discard washed impurities.

Why is HCl used instead of just deionized water?

HCl is a much stronger acid which protonates the amine group of the p-phenetidin, which makes it more soluble in the solution

What makes a molecule a chromophore?

Highly conjugated characteristic group like azo (N=N), nitro (NO2), or carbonyl (C=O)

How are the compounds on the TLC plate visualized?

If they are colored no additional visualization method is required. If not, place under UV light which activates a fluorescent indicator on the plates

In our EAS iodination what is our source of iodine and what is our source of an oxidizer?

Iodine source= sodium iodine Oxidizer= household bleach/sodium hypochlorite/NaOCl

What effect does insoluble impurities like sand and glass have on MP?

No effect

A teaching assistant found an old vial containing acetophenetidin synthesized by students from last semester. He measured its melting point to be 135.5-136.8C which is very close to the theoretical value. Can he confirm that the compound is acetophenetidin just from this information?

No, he would need to do a mixed melting point with some pure acetophenetidin

Could you separate 2,4-dinitrophenol (pH 3.96) from benzoic acid using extraction procedure IN THIS EXPERIMENT?

No, since both are very close in acidity; cannot use reagents in this experiment to neutralize one and keep one (stronger acid) as a weak acid; both would be neutralized

How can you tell enough MgSO4 has been used to dry the organic layer after the extraction? A. The MgSO4 color will change to a gray color B. There is no visible way you can tell C. None of these are correct D. The MgSO4 will dissolve into solution

None of these are correct Book says to continue to add until it flows freely and no longer clumps together

Which fabric were most resistant to dyeing?

Orlon did not react well. Looking at the structures,there are few areas for the dye to react.

What is the purpose of the sodium acetate solution in the amide synthesis?

Sodium acetate creates a buffer within the reaction that would control HCl's acidity

How to remove reddish brown color from p-phenetidine?

Purify using activated carbon

What factor controls the rate of movement of bands in chromatography?

Rates depend on interactions with the stationary phase Slower- if component has greater affinity for stationary phase (more polar) Faster- if component has greater affinity for mobile phase (more nonpolar)

What is the purpose of the 6% sodium hypochlorite solution (the oxidizer)

React with sodium iodine to form strong electrophile that would now react with the salicylamide in the EAS reaction

How is the Rf value calculated? Predict the Rf values for polar and non polar compounds.

Rf= (distance from origin to center of spot/ distance from origin to solvent front) Polar=small Rf value Nonpolar= Rf value close to 1

What Nobel Prize winner's work was refuted based on melting point?

Robert Robinsons synthesis of phystigmine was refuted by Percy Julian due to its uncharacteristic melting point

What do seed crystals do?

Serve as nucleation sites where more molecules of the desired compound attach and layer

How is slime made?

Slime is a cross-linked polymer formed from the reaction of poly(vinyl alcohol) with borax

Why is a 50:50 ratio the best for this case?

The 50:50 ratio was enough to separate the polar and non polar compounds of the spinach.

When doing a catalytic hydrogenation on gestrinone in the synthesis of tetrahydrogestrinone (THG), shown below, why are the alkenes not reduced?

The alkenes are conjugated, lowering their reactivity. So only alkyne is reduced (adding 4 hydrogens)

What is present in the aqueous layer you drained? How do you neutralize it? How do you isolate it?

The carboxylate ion is present. In order to regenerate the carboxylic acid it must be added to HCl in an ice bath to induce crystallization. To isolate the crystals, vacuum filtration is performed.

Why does the presence of a soluble impurity in a sample has the effect of lowering and broadening the melting point range?

The impurity disrupts the crystalline lattice of the sample so less energy is required to convert the solid phase into a liquid phase

T or F: Inaccurate melting point determinations are often made due to poor heat transfer to the sample

True

Lady Tasting Coffee Case Study

The lady in question (Muriel Bristol) claimed to be able to tell whether the tea or the milk was added first to a cup. Fisher proposed to give her eight cups, four of each variety, in random order and she had to come within < 5% to reject null hypothesis.

Why is phenol much more acidic than cyclohexanol

The more stable or the weaker the conjugate base, the more acidic the compound is. When losing a proton, phenol's conjugate base has resonance stability from its aromatic ring.

What is present in the organic layer? What steps do you need to take to isolate the desired product?

The phenol is present. There may be some water present in the solution so it must be dried with brine and anhydrous magnesium sulfate until it no longer clumps together. The drying agent is then separated from the organic solution through gravity filtration. Once this is done, the ether must be evaporated using Rotovap so that the pure phenol solid is left in the flask.

What do you change in chromatography to influence the speed at which compounds elute through the stationary phase

The ratio of solvents in the eluent mixture (tailoring the polarity of the solvents)

Anhydrous Magnesium Sulfate

The salt absorbs the water that is dissolved in the organic solvent.

What is the purpose of the sodium carbonate in Part 1A? Why do we add glacial acetic acid in Part 1B when we react with N,N-dimethylaniline, but we don't use it with the other aromatic compounds?

The sodium carbonate deprotonates HSO3- making the sulfonic acid soluble The purpose of the glacial acetic acid is to act as a catalyst to partially protonate aniline to activate it for reaction with diazonium salt. We don't use it with the other aromatic coupling reagents because they are already activated.

What criteria must be met in order for a liquid-liquid extraction to be successful?

The two solvents that are chosen for the extraction must be immiscible. In addition, the compound to be extracted must have different affinities for the two solvents.

When dyeing with your azo dye, which fibers seemed to interact best with the dye? Explain your results.

The wool interacted best due to its amino group and carbonyl group The azo dye we created has polar sulfonate groups that interact well with other polar sites in the fiber

What is the purpose of boiling chips/wooden sticks during the recrystallization process?

They help avoid "bumping" of liquid

How does dye fix to fabric?

Through various intermolecular forces (van der Waals, H bonding, covalent bonds)

During check-in you found a beaker in your drawer that is cracked and has some white solid on the side. You should...

Throw it in the hazardous solid waste container

What was the best recrystallization solvent for the acetophenetidin?

Water because the solute is completely soluble at boiling point, but the crystals reappear when solution is placed in an ice bath.

When we make Nylon-10,6 why don't we use the dicarboxylic acid that is typically used in industry? What do we use instead?

We used a diacid chloride (sebacoyl chloride) because it is more reactive

Do you expect xanthophylls to be more or less polar than B-carotene? Why?

Xanthophylls are more polar due to the very polar alcohol group

What kind of polymerization reaction do we use to produce Nylon-10,6?

a condensation polymerization between sebacoyl chloride and hexamethylene diamine In this case an amide linkage forms between an acid halide and an amine with the elimination of HCl

monomer

a molecule/segment of molecular structure that is repeated many times in a polymer

What were the uses of acetophenetidin?

analgesic and antipyretic (pain and fever relief)

During TLC, the components of the sample mixture pass through the stationary phase as _________

bands or areas of concentration

How does the eluent move up the TLC plate?

by capillary action the sample components are carried with it and separated on the stationary phase

Why would you use AlCl3 for a chlorination or bromination EAS but not for an iodination? What must you use for an iodination?

iodine is less reactive Requires the use of an oxidizing agent

What does the origin line indicate on the TLC plate? What should you use to mark the origin line? Why?

indicates the starting point of the sample Use pencil because pen ink is polar meaning that the ink will run with the TLC solvent

Theoretical Yield (in grams)

moles of limiting reagent x molecular weight of product

The melting point of a pure compound is...

narrow- one or two degrees impurities lower and broaden the melting point ranges

How do electron donating groups direct incoming groups?

ortho or para positions

What is the amide synthesis of acetophenetidin reaction?

p-phenetidine + acetic anhydride (solvent: Sodium acetate and hydrochloric acid)

repeating unit

part of the polymer whose repetition produces the complete polymer chain except for the end groups

Why is the sample of p-phenetidine reddish brown?

small amount of impurities caused by air oxidation of the amino functional group

What is the purpose of recrystallization?

purify organic solids

Limiting reagent

reactant that determines amount of product that can be formed; entirely used in the reaction

What is chromatography? What are some examples?

refers to techniques for separating, analyzing, and identifying compounds examples-thin layer (TLC), gas (GC), and high performance liquid chromatography (HPLC)

What is the purpose of sodium thiosulfate in our iodination of salicylamide?

removes residual iodine from the solution

You will synthesize Nylon-10,6 using interfacial polymerization. Will sebacoyl chloride be on top or will hexamethylene diamine/NaOH be on top?

sebacoyl chloride on top of hexamethylene diamine/NaOH nylon film forms at interface (where the two liquids meet)

Cancer Cure or Conservation Case Study

taxol drug made from bark of red cedar tree found on Quinault Indian tribal land drug used for ovarian/breast cancer treatment

What is the melting point range? What is it used for?

temperature at which the first drop of a liquid is observed until all of solid is liquified Unique property of that compound and is used in identification and assessment of purity

condensation polymerization

the joining of monomers with the loss of a small molecule (like water/HCl)

What is the solvent front?

the leading edge of the solvent

OLED Case Study

the more conjugated a compound is the bigger wavelength (aka visible light) it absorbs because less energy is required to excite electrons from HOMO to LUMO due to small gap

What is the mobile phase in TLC?

the phase that carries the mixture through the stationary phase eluent (hexane/ethyl acetate solution)

What is the stationary phase in TLC?

the phase that is fixed in place in chromatography plate silica gel

How is the melting point of a pure substance defined?

the temperature at which the solid phase is in equilibrium with the liquid phase.

Why should you not stir the crystals in the buchner funner?

this makes the filtration less efficient and does not adequately remove the solvent from the crystal

Why is NaOH added during the condensation polymerization of Nylon-10,6?

to neutralize the HCl eliminated each time a new amide bond is formed