What is the name of the reaction when acetamide is converted to methylamine?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Hofmann Bromamide degradation reaction
The Hofmann bromamide degradation converts an amide into a primary amine with one carbon less:
\( \displaystyle \ce{R-CONH2 + Br2 + 4NaOH -> R-NH2 + Na2CO3 + 2NaBr + 2H2O} \)
Acetamide (two carbons) gives methylamine (one carbon):
\( \displaystyle \ce{CH3CONH2 + Br2 + 4NaOH -> CH3NH2 + Na2CO3 + 2NaBr + 2H2O} \)
Why the other options are incorrect
Option (1) Friedel-Crafts alkylation — Incorrect. This puts an alkyl group on a benzene ring using an alkyl halide and anhydrous \( \ce{AlCl3} \): \( \ce{C6H6 + CH3Cl} \xrightarrow{\text{anhyd. }\ce{AlCl3}} \ce{C6H5CH3 + HCl} \). No amine is involved.
Option (2) Gabriel phthalimide synthesis — Incorrect. It also gives primary amines, but from an alkyl halide and potassium phthalimide, followed by alkaline hydrolysis, not from an amide; no carbon is lost.
Option (4) Carbylamine Reaction — Incorrect. This is a test for primary amines: heating with chloroform and ethanolic KOH gives a foul-smelling isocyanide, \( \ce{R-NH2 + CHCl3 + 3KOH -> R-NC + 3KCl + 3H2O} \).
NCERT (2026-27 edition):
Hoffmann Bromamide Degradation Reaction
