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Which of the following nitrogen-containing compounds gives a primary amine (R–NH2) on treatment with bromine and concentrated KOH, i.e., under Hofmann rearrangement conditions?

1. RCONHCH3
2. RCOONH4
3. RCONH2
4. R–CO–NHOH

Correct answer: RCONH2

Solution

The Hofmann bromamide degradation requires a primary (unsubstituted) amide: RCONH2 + Br2 + 4KOH -> RNH2 + 2KBr + K2CO3 + 2H2O, giving an amine with one fewer carbon. N-substituted amides and the others do not undergo it.

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