Which of the following compounds gives a foul-smelling product when heated with chloroform and ethanolic potassium hydroxide?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → C2H5NH2
This is the carbylamine reaction (isocyanide test). A primary amine, R–NH2, heated with chloroform and ethanolic KOH gives an isocyanide (carbylamine), a foul-smelling substance. Ethanamine is a primary amine:
\( \displaystyle \ce{C2H5NH2 + CHCl3 + 3KOH} \xrightarrow{\text{heat}} \ce{C2H5NC + 3KCl + 3H2O} \)
The product, ethyl isocyanide, has the foul smell.
Why the other options are incorrect
Option (1) (C2H5)2NH — Incorrect. N-Ethylethanamine is a secondary amine; secondary amines do not give this reaction.
Option (2) (CH3)3N — Incorrect. Trimethylamine is a tertiary amine; it has no N–H bond and does not give this reaction.
Option (4) CH3CN — Incorrect. Ethanenitrile is a nitrile, not an amine; it has no –NH2 group to react.
NCERT (2026-27 edition):
9.6 Chemical Reactions – “4. Carbylamine reaction
Aliphatic and aromatic primary amines on heating with chloroform and ethanolic potassium hydroxide form isocyanides or carbylamines which are foul smelling substances.”