To convert ethanamide into methanamine which of the following reagents can be used?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Br2 and NaOH
Ethanamide (\( \ce{CH3CONH2} \)) has two carbon atoms and methanamine (\( \ce{CH3NH2} \)) has one, so the reagent must remove one carbon atom. This is the Hofmann bromamide degradation: an amide treated with bromine and an aqueous or ethanolic solution of NaOH gives a primary amine with one carbon atom less; the carbon of C=O leaves as carbonate:
\( \displaystyle \ce{CH3CONH2 + Br2 + 4NaOH -> CH3NH2 + Na2CO3 + 2NaBr + 2H2O} \)
Why the other options are incorrect
Option (1) LiAlH4, H2O — Incorrect. It reduces the C=O group to \( \ce{CH2} \) without losing carbon, giving ethanamine, \( \ce{CH3CH2NH2} \).
Option (2) H2/Ni, Na(Hg)/C2H5OH — Incorrect. These reduce nitriles (and amides) to amines with the same number of carbon atoms.
Option (4) Sn and HCl — Incorrect. It reduces nitro compounds to amines (e.g. nitrobenzene to aniline), not amides.
NCERT (2026-27 edition):
Hoffmann Bromamide Degradation Reaction
