question

Which of the following statements is not correct? a. The first step in the Fischer esterification is the protonation of the carbonyl carbon of the carboxylic acid. b. Alkyl acid chlorides show a very exothermic reaction with water. c. The product of the ammonolysis of benzoyl chloride is benzamide. d. Esters, acid chlorides, ethers, and amides are all derivatives of carboxylic acids. e. None of these are correct.

answer

d. Esters, acid chlorides, ethers, and amides are all derivatives of carboxylic acids. is FALSE (amides are NOT)

question

What is the structure of an azo dye?

answer

phenyls connected by N=N

question

The Grignard reagent, n-butylmagnesium bromide, may be classified as a:

answer

carbon nucleophile (H?C-CH?-CH?-CH-Br? Mg?)

question

The analogy between a chemical bond and a mechanical spring is very approximate, since electrons and atoms are governed by ____________.

answer

quantum mechanics

question

Why is UVC sunlight less dangerous to humans than UVB even if the energy of UVC radiation is higher?

answer

The UVC radiation is absorbed by ozone in the earth's atmosphere but UVB is not.

question

In the nitration of methyl benzoate, which step is rate determining under the conditions used in the lab?

answer

addition of the electrophile to the benzene ring

question

What type of bond links amino acids together to make peptides?

answer

an amide bond

question

A compound that gives positive 2,4-DNP results, negative iodoform test results, and positive Tollens' test results must have:

answer

2,4-DNP: test for aldehydes AND ketones iodoform: test for methyl ketones, alcohols (ethanol) Tollens': test for aldehydes NOT KETONES must have an aldehyde, but no methyl ketone (ex: benzaldehyde)

question

Which is the best solvent choice for TLC? a. 10% ethyl acetate, 90% hexane Rf values: 0.12, 0.07, 0.01 b. 20% ethyl acetate, 80% hexane Rf values: 0.34, 0.29, 0.05 c. 30% ethyl acetate, 70% hexane Rf values: 0.53, 0.42, 0.10 d. 40% ethyl acetate, 60% hexane Rf values: 0.72, 0.61, 0.25 e. 50% ethyl acetate, 50% hexane Rf values: 1.0, 0.8, 0.7

answer

d. 40% ethyl acetate, 60% hexane causes most spread out results a: ?0.05, ?0.06 ? 0.11 b: ?0.05, ?0.24 ? 0.29 c: ?0.11, ?0.32 ? 0.43 d: ?0.11, ?0.36 ? 0.47 e: ?0.2, ?0.1 ? 0.3

question

When a molecule absorbs UV or visible light, what transition takes place?

answer

electrons in lower molecular orbitals are excited into orbitals of higher energy

question

formation of TPCP from benzil and dibenzyl ketone

answer

pic: benzil dibenzyl ketone: 1,3-diphenylacetone attacks of carbonyls to form pentyl ring, then reduction of hydroxyl groups to form alkenes IMPOSSIBLE: -OH group next to the carbonyl that remains in TPCP. That carbonyl is from dibenzyl ketone. The two oxygens that are next to each other are from benzil, and both are eventually reduced into alkenes.

question

Which combination of reagents will form a secondary alcohol?

answer

a Grignard reagent and an aldehyde (if the Grignard reagent is active in the middle of the molecule and not an an end)

question

Which of the following is not a polyamide? a. wool b. silk c. nylon d. aramid e. cotton

answer

e. cotton is NOT a polyamide wool, silk, nylon, aramid ARE polyamides

question

Which of the following aldol condensation reactions gives more than two aldol products? a. CH?CHO + CH?CH?CHO b. C?H?CHO + CH?CH?CHO c. C?H?CHO + C?H?CH?CHO d. HCHO + (CH?)?CHCHO e. PhCH?COCH?Ph + PhCO?Ph

answer

a. CH?CHO + CH?CH?CHO b,c,d: presence of phenyl rings limit the number of possible products d: formaldehyde limits number of possible products.

question

In the preparation of methyl benzoate (MW=136), a student started with 24.4 g of benzoic acid (MW=122) and 37.5 mL of methyl alcohol (MW=32, density=0.8 g/mL). After separation and purification, 11.6 g of methyl benzoate was obtained and 5.4 g of benzoic acid was recovered. What is the percent yield based on the amount of benzoic acid actually consumed?

answer

55% 37.5*0.8/32 = 0.9375 mol (24.4-5.4)/122 = 0.156 mol ? Limiting Reagent 0.156 mol * 136 g/mol = 21.18 g (theoretical yield) 11.6/21.18 = 0.55 0.55*100=55%

question

The nitration of methyl benzoate proceeds through which mechanism?

answer

Electrophilic Aromatic Substitution

question

What group cannot be easily reduced with NaBH??

answer

esters/carboxylic acids (ketones and aldehydes are OK)

question

A KMnO? test on the basic hydrolysis products of aspartame will detect the presence of

answer

methyl alcohol

question

Which of the following statements is NOT an important practice in maximizing the yield in a Grignard synthesis? a. All reactants, solvents, and reagents should be dry. b. The alkyl halide should be added to the Mg only fast enough to maintain reflux. c. The carbonyl compound should be added quickly to the Grignard reagent. d. The Mg salts formed during hydrolysis should be decomposed with a dilute acid. e. All of these are necessary practices.

answer

c. The carbonyl compound should be added quickly to the Grignard reagent. (The carbonyl should be added slowly to keep it at gentle reflux in order to prevent vapors from escaping.)

question

In the aldol reaction, OH? is a(n):

answer

catalyst

question

Which two amino acids have side chains involved in the deprotonation/protonation of mandelate in the active site of the enzyme Mandelate racemase?

answer

histidine, arginine(?)

question

The most likely oxidation contaminant found in a sample of an aldehyde is:

answer

a carboxylic acid

question

The Fischer esterification of benzoic acid with ethanol yields ethyl benzoate (ester) as the product. What intermediate is involved in the formation of ethyl benzoate?

answer

Ph-(HO-C-OH)-O-CH?CH? Hydrogen transferred from ethanol to carbonyl oxygen of benzoic acid. Product (ethyl benzoate) in pic.

question

By definition, a kinetic product _____, while a thermodynamic product _____.

answer

kinetic product: forms most quickly thermodynamic product: is the most stable product

question

Why is isoborneol the major product in the reduction of camphor with borohydride?

answer

The bulky borohydride ion can approach the camphor more easily from the less hindered endo side. (pic: camphor; isoborneol is the same, but with the C=O now a C-OH)

question

Which of the following is NOT present in the equilibrium of a Fischer esterification reaction? a. carboxylic acids b. esters c. water d. alcohol e. aldehyde

answer

e. aldehyde is NOT present

question

The active site Mandelate racemace involves the presence of a non-protein species in the active site to which you measured some bond distances. That species (called a prosthetic group) was:

answer

Mg²?

question

You have a compound that has a carbonyl group, but you don't know if it is a carboxylic acid or an aldehyde. Which of the following tests would NEVER provide useful information to distinguish between the two possibilities? a. 2,4-DNP test b. Tollens' test c. Schiff's test d. Aqueous Sodium Bicarbonate test e. Ninhydrin test

answer

e. Ninhydrin test 2,4-DNP test: aldehydes and ketones Tollens' test: aldehydes Schiff's test: aldehydes Aqueous Sodium Bicarbonate test: carboxylic acids Ninhydrin test: ammonia groups

question

The absorbance of a compound with a concentration 7.5 mM at 330 nm is 1.5. If the path length was 1 cm, what is the molar extinction coefficient of the compound at 330 nm?

answer

200 M?¹cm?¹

question

The electrophile for nitration of an aromatic compound is:

answer

NO??

question

The reaction that changes camphor to isoborneol using sodium borohydride is best described as a(n):

answer

reduction (C=O ? C-OH)

question

A purple color develops as soon as all reactants are mixed together for the aldol condensation of benzil and dibenzyl ketone. This color is due to:

answer

the production of a highly conjugated molecule

question

Which of the following statements is FALSE? a. Many low molecular weight carboxylic acids have an unpleasant smell. b. Esters in fragrances can slowly hydrolyze back to their original alcohol and acid. c. Low molecular weight alcohols have a fruity odor. d. Most low molecular weight esters are pleasant smelling. e. Sulfuric acid is used as a catalyst in the Fischer esterification reaction.

answer

c. Low molecular weight alcohols have a fruity odor is FALSE. Low molecular weight ESTERs have a fruity odor. Low MW alcohols smell like ethanol.

question

What reagent was used to reduce indigo (dark purple) to leucoindigo (colorless) in the experiment preparing indigo dye?

answer

10% sodium dithionite

question

In the reaction catalyzed by Diphosphomevalonate decarboxylase what type of reactive intermediate is generated?

answer

A carbocation

question

Only one major product is observed in the nitration of methyl benzoate. This is due to:

answer

the relatively low reactivity of the ortho and para positions

question

You are in lab, and you have already synthesized your indigo dye. You are heating your solution in a capped erlenmeyer flask. You have added sodium dithionite and have gotten a clear yellow solution. However, as your solution heats, you notice that blue keeps creeping up the side of your flask, no matter how much sodium dithionite you add, but your solution is still clear yellow. Why is this?

answer

There is a leak into your flask and the leucoindigo is being oxidized.

question

In the addition of the HBr to butadiene, what is the thermodynamic product?

answer

1-bromo-2-butene (Br-CH?-CH=CH-CH?)

question

Which of the following compounds could be used as a solvent for a Grignard reaction? a. CH?OCH?CH?OCH? b. H?O c. CH?CH?COOH d. CH?C?CH e. (CH?)?C-OH

answer

a. CH?OCH?CH?OCH? (an ester. all of the other choices have acidic hydrogens, attached to oxygens or double/triple bonded carbons)

question

How can amide bonds be hydrolyzed? >acidic conditions >basic conditions >neutral conditions >acidic or basic conditions

answer

either by acidic or basic conditions

question

What does iodoform test give a positive result for?

answer

methyl ketones, or the CH?CH?(OH)R group, which can be oxidized to a methyl ketone (CH?CHOR) such as in 2-hexanol

question

What two processes were catalyzed by the enzymes investigated in the Visualization of Proteins experiment?

answer

racemization & decarboxylation

question

Which of the following has the lowest ?max value? a. Benzene b. Naphthalene c. Avobenzone d. cyclohexene e. Styrene

answer

d. Cyclohexene (has the least unsaturation at one double bond) benzene: 3 napthalene: 5 avobenzone: 6 styrene: 4

question

One mole of sodium borohydride can reduce theoretically how many moles of ketone?

answer

4 (sodium borohydride: NaBH?)

question

What is the definition for lachrymator?

answer

A substance with vapors that irritate the eye, causing shedding of tears.

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