Carbylamine reaction is used as a test for -

The correct answer is Option (2) → Primary Amines

In the carbylamine reaction, for example with an alkyl amine or with aniline:

    \( \displaystyle \ce{R-NH2 + CHCl3 + 3KOH} \xrightarrow{\text{heat}} \ce{R-NC + 3KCl + 3H2O} \)

    \( \displaystyle \ce{C6H5-NH2 + CHCl3 + 3KOH} \xrightarrow{\text{heat}} \ce{C6H5-NC + 3KCl + 3H2O} \)

To form the R–N≡C group, the nitrogen must lose both of its hydrogen atoms. Only a primary amine has two H atoms on nitrogen, so only it gives the reaction.

Why the other options are incorrect

• Option (1) Tertiary Amines — Incorrect. \( \ce{R3N} \) has no H on nitrogen, so no isocyanide can form.

• Option (3) Quaternary Amines — Incorrect. Quaternary ammonium salts (\( \ce{R4N^{+}X^{-}} \)) have no N–H and no lone pair on nitrogen.

• Option (4) Secondary Amines — Incorrect. \( \ce{R2NH} \) has only one H on nitrogen, not the two that are needed.

NCERT (2026-27 edition):
Carbylamine Reaction

Note: The same/similar question has been asked in different years by NTA as per the details given below: