The reaction of $\mathrm{R}-\mathrm{C}-\mathrm{NH}_{2}$ with bromine and KOH gives $\mathrm{RNH}_{2}$ as the end product. Which one of the following is the intermediate product formed in this reaction?

(C) $\mathrm{R}-\mathrm{N}=\mathrm{C}=\mathrm{O}$

(B) $\mathrm{R}-\mathrm{NH}-\mathrm{Br}$

JEE Main · 2022 · 25 Jun 2022 · Shift 1 · Aldehydes Ketones and Carboxylic Acids

The reaction of

R - C - NH_{2}

with bromine and KOH gives

RNH_{2}

as the end product. Which one of the following is the intermediate product formed in this reaction?

(A)(see structure)
(B) $R - NH - Br$
(C) $R - N = C = O$ ✓ Correct
(D)(see structure)

Answer: (C)

Solution

This is the Hofmann bromamide degradation reaction. A primary amide reacts with bromine in the presence of a strong base (KOH) to give a primary amine with one carbon less. The key intermediate in this reaction is the isocyanate (R-N=C=O), which is formed after the loss of bromide ion and rearrangement. The isocyanate then undergoes hydrolysis to give the amine. The correct answer is (C).

JEE Main · 2022 · 25 Jun 2022 · Shift 1 · Single correct option

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