Question

Identify false statement from following regarding preparation of amines by Hofmann degradation method.

• A. It is useful to convert amides to primary amines.
• B. In this -CO-group is reduced to \(-\text{CH}_2-\) group.
• C. Molar mass of the amine obtained is always less than the amide.
• D. The reagent used is \(\text{Br}_2\) and \(\text{KOH}_{(aq)}\) .

Hint:

Hofmann bromamide reaction removes the carbonyl carbon as carbonate; it does not reduce it.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
In Hofmann bromamide degradation: \(\text{R-CONH}_2 + \text{Br}_2 + 4\text{KOH} \rightarrow \text{R-NH}_2 + \text{K}_2\text{CO}_3 + 2\text{KBr} + 2\text{H}_2\text{O}\).

Step 2: Check (A), (C), (D):
(A) An amide is converted to a primary amine, true.
(C) The amine has one carbon fewer than the amide, so its molar mass is lower, true.
(D) The reagent is \(\text{Br}_2\) with aqueous KOH, true.

Step 3: Check (B):
The carbonyl carbon is lost as carbonate through an isocyanate intermediate. It is not reduced to \(\text{-CH}_2-\). Reduction of the carbonyl to \(\text{CH}_2\) happens when amide is reduced with \(\text{LiAlH}_4\), giving an amine with the same number of carbons. So (B) is false.

Final Answer:
The false statement is (B). \[ \boxed{\text{(B)}} \]