Identify the name of the given reaction:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Carbylamine reaction
A primary amine heated with chloroform and alcoholic KOH gives an isocyanide (carbylamine) with a very offensive smell; secondary and tertiary amines do not, so this is a test for primary amines.
\( \ce{R-NH2 + CHCl3 + 3KOH} \xrightarrow{\Delta} \ce{R-NC + 3KCl + 3H2O} \)
Why the other options are incorrect
Option (1) Sandmeyer’s reaction — Incorrect. The –\( \ce{N2+} \) group of a diazonium salt is replaced by Cl, Br or CN using copper(I) salts; no chloroform is used.
\( \ce{ArN2+Cl-} \xrightarrow{\ce{CuCl/HCl}} \ce{ArCl + N2} \)
Option (3) Hoffmann Bromamide reaction — Incorrect. An amide with \( \ce{Br2} \) and NaOH gives a primary amine with one carbon less; here an amine is the reactant, not the product.
\( \ce{RCONH2 + Br2 + 4NaOH -> RNH2 + Na2CO3 + 2NaBr + 2H2O} \)
Option (4) Hinsberg’s reaction — Incorrect. Amines react with benzenesulphonyl chloride to give sulphonamides, not isocyanides.
\( \ce{C6H5SO2Cl + RNH2 -> C6H5SO2NHR + HCl} \)
NCERT (2026-27 edition):
Carbylamine Reaction
