An aromatic compound (A) on treatment with aqueous ammonia and heating forms compound (B) which on heating with Br2 and KOH forms a compound (C) of molecular formula C7H7NO.
Identify the reaction taking place while converting compound B to compound C in the following reaction sequence:
Reaction Scheme:
C₆H₅COOH —(i) aq. NH₃, (ii) Δ→ B —(Br₂ / KOH)→ C
Answer & explanation
Correct answer: option 3
The correct answer is option 3. Hofmann Bromamide reaction.
Step 1:
Benzoic acid reacts with aqueous ammonia and on heating forms benzamide.
Reaction:
$C_6H_5COOH + NH_3 \rightarrow C_6H_5CONH_2 \text{ (Benzamide)}$
So compound $B = \text{Benzamide}$.
Step 2:
Benzamide reacts with $Br_2$ and $KOH$. This reaction converts amide into amine with one carbon less. This reaction is known as Hofmann bromamide degradation or Hofmann rearrangement.
Reaction:
$C_6H_5CONH_2 + Br_2 / KOH \rightarrow C_6H_5NH_2 \text{ (Aniline)}$
So compound $C = \text{Aniline}$.
This reaction involves rearrangement of amide to amine with loss of carbonyl carbon as $CO_2$.
Therefore, the reaction converting $B$ to $C$ is Hofmann bromamide reaction.