Question 1

Which of the following statements best explains why carboxylate ions do not undergo nucleophilic acyl substitution reactions?

Accepted Answer

The negative charge on the carboxylate ion repels nucleophiles, preventing attack on the carbonyl carbon.

Question 2

In the Fischer esterification reaction, which reagent is used in excess to drive the reaction toward ester formation?

Accepted Answer

Excess alcohol

Question 3

Which of the following is the correct balanced equation for the Fischer esterification of butanoic acid with methanol?

Accepted Answer

$$ \mathrm{CH_3CH_2CH_2COOH} + \mathrm{CH_3OH} \xrightarrow{HCl} \mathrm{CH_3CH_2CH_2COOCH_3} + \mathrm{H_2O} $$

Question 4

During the Fischer esterification mechanism, which atom in the alcohol attacks the carbonyl carbon of the carboxylic acid?

Accepted Answer

The oxygen atom of the alcohol

Question 5

When $$^{18}O-$$labeled methanol reacts with benzoic acid in a Fischer esterification, where does the $$^{18}O $$label end up?

Accepted Answer

In the ester product

Question 6

What is the product when a carboxylic acid reacts with a primary amine?

Accepted Answer

An ammonium carboxylate salt

Question 7

Which of the following carboxylic acid derivatives is most reactive toward nucleophilic acyl substitution?

Accepted Answer

Acyl chloride ($$ \mathrm{RCOCl} )$$

Question 8

Why does excess alcohol drive the Fischer esterification reaction to the right?

Accepted Answer

It shifts the equilibrium toward ester formation by Le Chatelier's principle.

Question 9

Which of the following is a necessary condition for carboxylic acids to undergo nucleophilic acyl substitution?

Accepted Answer

They must be in their acidic form.

Question 10

In the reaction between a carboxylic acid and an amine, what type of reaction occurs?

Accepted Answer

An acid-base reaction

Question 11

Which of the following best describes the role of the acid catalyst in Fischer esterification?

Accepted Answer

It protonates the carbonyl oxygen, increasing the electrophilicity of the carbonyl carbon.

Question 12

Which of the following is the correct structure for acetic acid?

Accepted Answer

$$ \mathrm{CH_3COOH} $$

Question 13

Which of the following is NOT a product of the reaction between butanoic acid and methanol in the presence of HCl?

Accepted Answer

Butanoic acid

Question 14

What is the main reason carboxylic acids are less reactive than acyl chlorides in nucleophilic acyl substitution reactions?

Accepted Answer

Carboxylic acids have a poor leaving group (hydroxide ion).

Question 15

Which of the following is the correct product when acetic acid reacts with ethanol in the presence of an acid catalyst?

Accepted Answer

$$ \mathrm{CH_3COOCH_2CH_3} $$

Question 16

Which of the following is a plausible reason why the water produced in Fischer esterification with $$^{18}O-$$labeled methanol is unlabeled?

Accepted Answer

The $$^{18}O $$from methanol ends up in the ester, not in the water.

Question 17

Which of the following best describes the initial step in the mechanism of Fischer esterification?

Accepted Answer

Protonation of the carbonyl oxygen

Question 18

Which of the following is the correct name for the product formed from the reaction of butanoic acid and methanol?

Accepted Answer

Methyl butanoate

Question 19

In the reaction between a carboxylic acid and an amine, what is the charge on the nitrogen atom in the product?

Accepted Answer

Positive

Question 20

Which of the following is a key difference between the reaction of a carboxylic acid with an alcohol and with an amine?

Accepted Answer

Reaction with alcohol forms an ester, while reaction with amine forms an ammonium carboxylate salt.

Reactions of Carboxylic Acids and Their Derivatives

Study Guide - Practice Questions