Consider the following statements about some reactions of amines.
(A) Aliphatic and aromatic primary amines on heating with chloroform and ethanolic potassium hydroxide form foul smelling isocyanides.
(B) The carbylamine reaction is used as a test for secondary amines.
(C) A primary amine behaves as a nucleophile and can further react with an alkyl halide to form secondary and tertiary amines, and finally a quaternary ammonium salt.
(D) The number of hydrogen atoms attached to the nitrogen atom decides the course of reaction of amines, so primary, secondary and tertiary amines differ in many reactions.
Which of the statements given above are correct? Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A), (C) and (D) only
Amines react through the unshared electron pair on nitrogen, and the number of hydrogen atoms on nitrogen decides which reactions a primary, secondary or tertiary amine can give.
(A) Aliphatic and aromatic primary amines on heating with chloroform and ethanolic potassium hydroxide form foul smelling isocyanides. — True. This is the carbylamine reaction; the –NH2 group becomes the –NC group:
\( \displaystyle \ce{R-NH2 + CHCl3 + 3KOH} \xrightarrow{\text{Heat}} \ce{R-NC + 3KCl + 3H2O} \)
(B) The carbylamine reaction is used as a test for secondary amines. — False. Secondary and tertiary amines do not show this reaction.
It is a test for primary amines.
(C) A primary amine behaves as a nucleophile and can further react with an alkyl halide to form secondary and tertiary amines, and finally a quaternary ammonium salt. — True. Each amine formed still has an unshared pair on nitrogen, so it attacks another molecule of the alkyl halide (alkylation):
\( \displaystyle \ce{R-NH2} \xrightarrow{\ce{R-X}} \ce{R2NH} \xrightarrow{\ce{R-X}} \ce{R3N} \xrightarrow{\ce{R-X}} \ce{R4N^+X^-} \)
(D) The number of hydrogen atoms attached to the nitrogen atom decides the course of reaction of amines, so primary, secondary and tertiary amines differ in many reactions. — True. For example, the carbylamine reaction needs the two hydrogen atoms of an –NH2 group, so only primary amines give it.
NCERT (2026-27 edition):
9.6 Chemical Reactions – “Aliphatic and aromatic primary amines on heating with chloroform and ethanolic potassium hydroxide form isocyanides or carbylamines which are foul smelling substances. Secondary and tertiary amines do not show this reaction. This reaction is known as carbylamine reaction or isocyanide test and is used as a test for primary amines.”
9.4 Preparation of Amines – “The primary amine thus obtained behaves as a nucleophile and can further react with alkyl halide to form secondary and tertiary amines, and finally quaternary ammonium salt.”
9.6 Chemical Reactions – “The number of hydrogen atoms attached to nitrogen atom also decides the course of reaction of amines; that is why primary (–NH2), secondary (>N–H) and tertiary amines (>N–) differ in many reactions.”