Question 1

Which reagent is commonly used to facilitate the formation of amides from carboxylic acids and amines, as shown in the provided mechanism?

Accepted Answer

DCC (dicyclohexylcarbodiimide)

Question 2

In the DCC-mediated amide synthesis, what is the primary role of DCC?

Accepted Answer

It activates the carboxylic acid by forming an O-acylisourea intermediate.

Question 3

What is the byproduct formed when DCC is used in the preparation of amides?

Accepted Answer

Dicyclohexylurea

Question 4

Which of the following best describes the nucleophile in the DCC-mediated amide formation reaction?

Accepted Answer

The amine ($$R'NH_2$)

Question 5

Why is DCC-mediated amide synthesis preferred over direct heating of carboxylic acids with amines?

Accepted Answer

It avoids the need for high temperatures and prevents the formation of side products.

Question 6

A chemist attempts to synthesize an amide from benzoic acid and methylamine using DCC. Which compound is expected as the main organic product?

Accepted Answer

$$C_6H_5CONHCH_3$$

Question 7

Which step in the DCC-mediated amide formation mechanism involves the nucleophilic attack of the amine?

Accepted Answer

Attack on the O-acylisourea intermediate

Question 8

What is the main limitation of using DCC in peptide synthesis in biological systems?

Accepted Answer

DCC can cause racemization of chiral centers.

Question 9

Which of the following best explains why water must be excluded from the DCC-mediated amide synthesis?

Accepted Answer

Water can hydrolyze the O-acylisourea intermediate, reducing yield.

Question 10

A student tries to synthesize an amide using DCC, but observes no product formation. Which of the following is the most likely reason?

Accepted Answer

The reaction mixture contained water, which hydrolyzed the activated intermediate.

Question 11

Which of the following is the correct balanced equation for the DCC-mediated synthesis of an amide from a carboxylic acid ($$RCOOH) $$and a primary amine ($$R'NH_2$)?

Accepted Answer

$$RCOOH + R'NH_2$ + DCC \rightarrow RCONHR' + dicyclohexylurea$$

Question 12

In a laboratory setting, why is dicyclohexylurea typically removed by filtration after the DCC-mediated amide synthesis?

Accepted Answer

It is insoluble in most organic solvents and precipitates out.

Question 13

Which of the following statements about the DCC-mediated amide formation mechanism is FALSE?

Accepted Answer

The amine attacks the carboxylic acid directly without activation.

Question 14

A pharmaceutical company is synthesizing an amide drug using DCC. Which safety concern is most relevant when handling DCC?

Accepted Answer

DCC is a known skin sensitizer and can cause allergic reactions.

Question 15

Which of the following best describes the fate of the carboxylic acid's hydroxyl group in the DCC-mediated amide synthesis?

Accepted Answer

It is replaced and incorporated into dicyclohexylurea.

Preparation of Amides: Mechanism and Applications

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