Consider the following statements about some reactions of amines.
(A) Aliphatic and aromatic primary and secondary amines react with acid chlorides, anhydrides and esters by nucleophilic substitution.
(B) Acylation of an amine can be considered as the replacement of a hydrogen atom of the –NH2 or >N–H group by an alkyl group.
(C) Methanamine reacts with benzoyl chloride to give N-methylbenzamide.
(D) Amines react with carboxylic acids at room temperature to form amides.
Which of the statements given above are correct? Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A) and (C) only
In acylation, the nitrogen of a primary or secondary amine uses its unshared electron pair to attack an acid chloride, anhydride or ester. The hydrogen on nitrogen is replaced by an acyl group (R–CO–), and the product is an amide.
(A) Aliphatic and aromatic primary and secondary amines react with acid chlorides, anhydrides and esters by nucleophilic substitution. — True. The amine acts as the nucleophile; for example, ethanamine and ethanoyl chloride give N-ethylethanamide:
\( \displaystyle \ce{C2H5NH2 + CH3COCl} \xrightarrow{\text{pyridine}} \ce{C2H5NHCOCH3 + HCl} \)
(B) Acylation of an amine can be considered as the replacement of a hydrogen atom of the –NH2 or >N–H group by an alkyl group. — False. The group brought in is an acyl group (R–CO–), not an alkyl group.
Bringing in an alkyl group is alkylation, which is done with alkyl halides.
(C) Methanamine reacts with benzoyl chloride to give N-methylbenzamide. — True. This acylation with benzoyl chloride is called benzoylation:
\( \displaystyle \ce{CH3NH2 + C6H5COCl -> CH3NHCOC6H5 + HCl} \)
(D) Amines react with carboxylic acids at room temperature to form amides. — False. A carboxylic acid gives its proton to the basic amine, so a salt is formed at room temperature, not an amide:
\( \displaystyle \ce{CH3NH2 + CH3COOH -> CH3NH3^+ CH3COO^-} \)
NCERT (2026-27 edition):
9.6 Chemical Reactions – “3. Acylation: Aliphatic and aromatic primary and secondary amines react with acid chlorides, anhydrides and esters by nucleophilic substitution reaction. This reaction is known as acylation. You can consider this reaction as the replacement of hydrogen atom of –NH2 or >N–H group by the acyl group. The products obtained by acylation reaction are known as amides.”
“Amines also react with benzoyl chloride (C6H5COCl). This reaction is known as benzoylation.”
“What do you think is the product of the reaction of amines with carboxylic acids? They form salts with amines at room temperature.”