Additional Problems 11: Carboxylic Acid Derivatives

Visualizing Chemistry

Problem 11.60
Name the following compounds:

(a)

Ball-and-stick model depicts four-carbon chain with N, N-dimethylamine, and methyl groups attached to first and third carbon. Black, gray, blue, and red spheres represent carbon, hydrogen, nitrogen, and oxygen, respectively.

(b)

The ball-and-stick model shows a carbonyl group with a benzene ring attached to one side and a four carbon chain bearing a methyl group on C3 on the other side.

Problem 11.61
How would you prepare the following compounds starting with an appropriate carboxylic acid and any other reagents needed? (reddish brown = Br.)

(a)

The ball-and-stick model shows a carbonyl group with an ortho substituted bromobenzene ring attached to one side and an isopropyl group on the other side.

(b)

Ball-and-stick model shows cyclopentane ring with a C H 2 C O N H 2 group as a side chain. The blue and reddish-brown spheres represent nitrogen and bromine, respectively.

Problem 11.62
The following structure represents a tetrahedral alkoxide-ion intermediate formed by addition of a nucleophile to a carboxylic acid derivative. Identify the nucleophile, the leaving group, the starting acid derivative, and the ultimate product (green = Cl).

Ball-and-stick model shows a five-carbon alkoxide chain where ammonia and chlorine are attached to the carbonyl carbon. The fourth and fifth carbons are double-bonded, with a methyl group on the fourth.

Problem 11.63
Electrostatic potential maps of a typical amide (acetamide) and an acyl azide (acetyl azide) are shown. Which of the two do you think is more reactive in nucleophilic acyl substitution reactions? Explain.

The electrostatic potential map and structure of acetamide and acetyl azide. The azide has a carbonyl group with a methyl group on one side and a chain of three nitrogen atoms on the other side. The nitrogens are double bonded to each other.

Mechanism Problems

Problem 11.64
Predict the product(s) and write the mechanism for the following reactions:

(a)

The reaction between ethyl propionate and ethyl amine in the presence of pyridine gives unknown products depicted by a question mark.

(b)

The reaction between a five-membered ring containing two carbonyl groups with an oxygen atom between them and sodium methoxide gives unknown products depicted by a question mark.

Problem 11.65
Predict the product(s) for the following reactions:

(a)

The reaction between cyclopentane carboxylic acid and thionyl chloride gives unknown products depicted by a question mark.

(b)

The reaction of but-2-enoic acid with thionyl chloride giving unknown products depicted by a question mark.

Problem 11.66
Predict the product(s) for each of the following reactions:

(a)

The reaction of ethyl-3-methyl butanoate with aqueous acid gives an unknown product depicted by a question mark.

(b)

The reaction of but-2-enoic acid with hydrochloric acid catalyst in methanol gives an unknown product depicted by a question mark.

Problem 11.67
Predict the product(s) for the following reactions:

(a)

The reaction of an ester with two equivalents of phenyl magnesium bromide in ether, followed by treatment with acid gives an unknown product depicted by a question mark.

(b)

The reaction of a four membered ring contaning a carbonyl group with an oxygen atom next to it with two equivalents of ethyl magnesium bromide in ether followed treatment with acid gives an unknown product depicted by a question mark.

Problem 11.68
Fats are biosynthesized from glycerol 3-phosphate and fatty-acyl CoA’s by a reaction sequence that begins with the following step. Show the mechanism of the reaction.

The reaction between glycerol-3-phosphate and fatty-acyl coenzyme A in the presence of glycerol-3-phosphate acyltransferase to form 1-acylglycerol-3-phosphate. The glycerol-3-phosphate contains three-carbon vertical chain in which hydroxyl is replaced by phosphate.

Problem 11.69
Bacteria typically develop a resistance to penicillins and other β-lactam antibiotics (see Chemistry Matters at the end of this chapter) due to bacterial synthesis of β-lactamase enzymes. Tazobactam, however, is able to inhibit the activity of the β-lactamase by trapping it, thereby preventing a resistance from developing.

Reaction of beta-lactamase and tazobactam generates a trapped beta-lactamase. The reaction proceeds through multiple steps. Tazobactam contain a four-membered lactam ring.

The first step in trapping is reaction of a hydroxyl group on the β-lactamase to open the β– lactam ring of tazobactam. Show the mechanism.

Problem 11.70
In the iodoform reaction, a triiodomethyl ketone reacts with aqueous NaOH to yield a carboxylate ion and iodoform (triiodomethane). Propose a mechanism for this reaction.

A triiodomethyl ketone is converted to a carbozylate ion by treatment with base and then acid. Triiodomethane is a byproduct.

Naming Carboxylic Acid Derivatives

Problem 11.71
Give IUPAC names for the following compounds:

(a)

The structure shows a substituted benzamide where a methyl group is attached to the para position in the benzene ring.

(b)

The structure shows six-carbon chain where C 1 is a carbonyl group with a chlorine atom attached to it. There is a double bond between C2 and C3 and an ethyl group on C4.

(c)

The structure shows a four-carbon chain where C 1 and C 4 are carbonyl groups. A methoxy group is also attached to each carbonyl carbon.

(d)

The structure shows a benzene ring attached to a three-carbon side chain, the third carbon along the chain being a carbonyl group to which an oxygen and then an isopropyl group are also attached.

(e)

The structure shows an amide with a four-carbon chain where the carbonyl carbon at C 1 is attached to an N-methyl amine. A bromine atom is attached to C 3.

(f)

The structure shows a cyclopentene ring with a methoxycarbonyl group attached to one of the carbons of the double bond.

(g)

The structure shows an ester where the carbonyl carbon is attached to a benzene ring on one side and, on the other side, to an oxygen itself attached to a benzene ring.

(h)

The structure shows a thioester where a benzene ring is attached to a central carbonyl carbon. A sulfur atom bound to an isopropyl group is also attached to the carbonyl carbon.

Problem 11.72
Draw structures corresponding to the following names:

(a) p-Bromophenylacetamide

(b) m-Benzoylbenzamide

(c) 2,2-Dimethylhexanamide

(d) Cyclohexyl cyclohexanecarboxylate

(e) Ethyl 2-cyclobutenecarboxylate

(f) Succinic anhydride

Problem 11.73
Draw and name compounds that meet the following descriptions:

(a) Three acid chlorides having the formula C6H9ClO

(b) Three amides having the formula C7H11NO

Nucleophilic Acyl Substitution Reactions

Problem 11.74
Predict the product, if any, of reaction between propanoyl chloride and the following reagents:

(a) LiAlH4, then H3O+

(b) CH3MgBr, then H3O+

(c) H3O+

(d) Cyclohexanol

(e) Aniline

(f) CH3CO2– Na+

Problem 11.75
Answer Problem 11.74 for reaction of the listed reagents with methyl propanoate.

Problem 11.76
Answer Problem 11.74 for reaction of the listed reagents with propanamide.

Problem 11.77
How might you prepare the following compounds from butanoic acid?

(a) 1-Butanol

(b) Butanal

(c) 1-Bromobutane

(d) Pentanenitrile

(e) Butene

(f) N-Methylpentanamide

(g) 2-Hexanone

(h) Butylbenzene

(i) Butanenitrile

Problem 11.78
Predict the product(s) of the following reactions:

(a)

The reaction of ethyl cyclohexanecarboxylate with ethylmagnesium bromide followed by treatment with acid to give an unknown product, denoted by a question mark.

(b)

The reaction of cyclopentanecarbonyl chloride with methyl amine to give an unknown product, denoted by a question mark.

(c)

The reaction of 2-methylcyclohexane carboxylic acid with methanol in the presence of sulfuric acid to give an unknown product, denoted by a question mark.

(d)

The reaction of methyl-3-methylpent-4-enoate with lithium aluminum hydride followed by treatment with acid to give a unknown product, denoted by a question mark.

(e)

The reaction of cyclohexanol with acetic anhydride in pyridine to form an unknown product, denoted by a question mark.

(f)

The reaction of 2-methylbenzamide with lithium aluminum hydride and then water to give an unknown product, denoted by a question mark.

(g)

The reaction of 2-(2-bromophenyl)acetic acid with thionyl chloride to form an unknown product, denoted by a question mark.

Problem 11.79
The following reactivity order has been found for the saponification of alkyl acetates by aqueous NaOH. Explain.

CH3CO2CH3 > CH3CO2CH2CH3 > CH3CO2CH(CH3)2 > CH3CO2C(CH3)3

Problem 11.80
Explain the observation that attempted Fischer esterification of 2,4,6-trimethylbenzoic acid with methanol and HCl is unsuccessful. No ester is obtained, and the acid is recovered unchanged. What alternative method of esterification might be successful?

Problem 11.81
Outline methods for the preparation of acetophenone (phenyl methyl ketone) starting from the following:

(a) Benzene

(b) Benzonitrile

(c) Styrene

Problem 11.82
Treatment of 5-aminopentanoic acid with DCC (dicyclohexylcarbodiimide) yields a lactam. Show the structure of the product of the reaction.

Problem 11.83
tert-Butoxycarbonyl azide, a reagent used in protein synthesis, is prepared by treating tert-butoxycarbonyl chloride with sodium azide. Propose a mechanism for this reaction.

The reaction of tert-butyl chloroformate with sodium azide forming an azide derivative in which the chlorine atom is replaced by an N 3 (azide) group at the carbonyl carbon.

Step-Growth Polymers

Problem 11.84
Qiana, a polyamide fiber with a silky texture, has the following structure. What are the monomer units used in the synthesis of Qiana?

Qiana has a repeating unit that comprises of a dicarbonyl group, an amide bond, and two methylene linked cyclohexane rings.

Problem 11.85
What is the structure of the polymer produced by treatment of β-propiolactone with a small amount of hydroxide ion?

The structure of beta-propiolactone comprises of a four-membered ring with a carbonyl group linked to an oxygen atom in the ring.

Problem 11.86
Polyimides with the structure shown are used as coatings on glass and plastics to improve scratch resistance. How would you synthesize a polyimide?

Polyimide structure in parentheses with subscript n shows benzene fused between two cyclopentane with N and two carbonyls. Cyclopentane ring is single-bonded to another benzene on right with free bond.

General Problems

Problem 11.87
The following reactivity order has been found for the basic hydrolysis of p-substituted methyl benzoates:

Y=NO2 > Br > H > CH3 > OCH3

How can you explain this reactivity order? Where would you expect Y=C≡N, Y=CHO, and Y=NH2 to be in the reactivity list?

Reaction of a para-substituted methyl benzoate with aqueous base to give the corresponding carboxylate ion and methanol. The substitutent at the para position is represented by the letter Y.

Problem 11.88
One frequently used method for preparing methyl esters is by reaction of carboxylic acids with diazomethane, CH2N2.

The reaction of benzoic acid and diazomethane gives methyl benzoate and molecular nitrogen.

The reaction occurs in two steps: (1) protonation of diazomethane by the carboxylic acid to yield methyldiazonium ion, CH3N2+, plus a carboxylate ion; and (2) reaction of the carboxylate ion with CH3N2+.

(a) Draw two resonance structures of diazomethane, and account for step 1.

(b) What kind of reaction occurs in step 2?

Problem 11.89
When an amide is formed from an acid chloride or an anhydride, two equivalents of base are required. However, when an ester is used as the starting material, only one equivalent of base is needed. Explain this reactivity in terms of basicity of the leaving groups.

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