An aromatic compound (A) on treatment with aqueous ammonia and heating forms compound (B) which on heating with ` Br_2` and ` KOH` froms a compound (C ) of the molecular formula ` C_6 H_7 N`. Write the structures and `IUPAC` names of compounds (A) . (B) and (C ).

Explanation

Step 1. To find out the structures of compounds 'B' and 'C'.
(i) Since compound 'C' with M.F. `C_(6)H_(7)N` is formed from compound 'B' on treatment with `Br_(2)+KOH` (i.e., Hofmann bromamide reaction), therefore, compound 'B' must be an amide and 'C' must be an amine. the only amine having the M.F. `C_(6)H_(7)N` is `C_(6)H_(5)NH_(2)` (aniline or benzenamine).
(ii) Since 'C' is aniline, therefore, the amide from which it is formed must be benzamide `(C_(6)H_(5)CONH_(2))`.
Thus, compound 'B' is benzamide.
The chemical equation showing the conversion of 'B' to 'C' is
`underset("Benzamide (B)"(M.F.=C_(7)H_(7)NO))(C_(6)H_(5)CONH_(2)) underset(("Hofmann bromamide reaction"))overset(Br_(2)//KOH)to underset("Benzenamine (C)"(M.F.C_(6)H_(7)N))(C_(6)H_(5)NH_(2))`
Step 2. To find out the structure of compound 'A'.
Since compound 'B' is formed from compound 'A' with aqueous ammonia and heating, therefore, compound 'A' must be benzoic acid or benzenecarboxylic acid.
`underset("Benzoic acid")(C_(6)H_(5)COOH) underset((ii)Delta)overset((i)Aq.NH_(3))to underset("Benzamide (B)")(C_(6)H_(5)CONH_(2))`.