JEE Main 2023 · 29 January · evening · Single correct · +4 / −1
Reaction of propanamide with Br₂/KOH(aq) produces :
- (a) Propanenitrile
- (b) Propylamine
- (c) Ethylnitrile
- (d) Ethylamine
Answer and solution
Answer (d) Ethylamine
Solution
Chemistry ma’am · 3 steps
Amide plus Br₂ and KOH is Hofmann degradation: the C=O carbon leaves, so count one carbon less.
- Name the reaction. A primary amide heated with Br₂ and aqueous KOH undergoes Hofmann bromamide degradation. It gives a primary amine with one carbon fewer than the amide.
- Where carbon goes. The amide is first brominated on nitrogen. The ethyl group then shifts from the carbonyl carbon to nitrogen, giving an isocyanate, C₂H₅-N=C=O. Hydrolysis removes the carbonyl carbon as CO₂, which ends up as K₂CO₃.
CH₃CH₂CONH₂ + Br₂ + 4KOH → CH₃CH₂NH₂ + K₂CO₃ + 2KBr + 2H₂O
- So. Propanamide has 3 carbons, so the product is the 2-carbon amine CH₃CH₂NH₂, ethylamine, option (d).
The idea to keep. Br₂/KOH on an amide means Hofmann degradation: you get RNH₂ with one carbon less. Reducing the amide with LiAlH₄ keeps every carbon instead.
Answer from the NTA final answer key. Solution by PrepWiser.