Positive carbylamine test is shown by :
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → p-Methylbenzylamine
The carbylamine reaction is given only by primary amines, aliphatic or aromatic. Heated with chloroform and ethanolic KOH they form isocyanides (carbylamines), which have a very unpleasant smell:
\( \ce{R-NH2 + CHCl3 + 3KOH} \xrightarrow{\Delta} \ce{R-NC + 3KCl + 3H2O} \)
p-Methylbenzylamine, \( \ce{CH3C6H4CH2NH2} \), has a free –\( \ce{NH2} \) group: it is a primary amine.
\( \text{p-}\ce{CH3C6H4CH2NH2 + CHCl3 + 3KOH} \xrightarrow{\Delta} \text{p-}\ce{CH3C6H4CH2NC + 3KCl + 3H2O} \)
Why the other options are incorrect
Option (1) N-Methylaniline — Incorrect. \( \ce{C6H5NHCH3} \) is a secondary amine; it has only one N–H and cannot give an isocyanide.
Option (2) N,N-Dimethylaniline — Incorrect. \( \ce{C6H5N(CH3)2} \) is a tertiary amine with no N–H.
Option (3) Triethylamine — Incorrect. \( \ce{(C2H5)3N} \) is a tertiary amine with no N–H.
NCERT (2026-27 edition):
Carbylamine Reaction
