An aromatic compound 'A' on treatment with aqueous ammonia and heating forms compound 'B' which on heating with Br_(2) and KOH forms a compound 'C' of molecular formula C_(6)H_(7)N. Write the structures and IUPAC names of compounds A, B and C.

An aromatic compound 'A' on treatment with aqueous ammonia and heating

1.	An aromatic compound 'A' on treatment with aqueous ammonia and heating forms compound 'B' which on heating with Br_(2) and KOH forms a compound 'C' of molecular formula C_(6)H_(7)N. Write the structures and IUPAC names of compounds A, B and C.
Answer» Solution :Step 1 : To find out the STRUCTURES of COMPOUNDS .B. and .C. (i) As the compound .C. with molecular formula `C_(6)H_(7)N` is formed from compound .B. on treatment with `Br_(2)+KOH` (i.e., Hoffmann bromamide REACTION), compound .B. must be an amide and .C. must be an amine. The amine having the molecular formula `C_(6)H_(7)N" is "C_(6)H_(5)NH_(2)` (aniline or benzenamine). (ii) Since .C. is aniline, the amide .B. from which it is formed must be benzamide `(C_(6)H_(5)CONH_(2))`. The chemical equation showing the conversion of .B. to .C. is `""underset(underset((M.F.=C_(7)H_(7)NO))("Benzamide (B)"))(C_(6)H_(5)CONH_(2)) underset("(Hoffmann bromamide reaction)")overset(Br_(2)//KOH)(rarr)underset(underset((M.F.=C_(6)H_(7)N))("Benzenamine (C)"))(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, compound .A. must be benzoic acid or benzenecarboxylic acid. ACIDS on treatment with `NH_(3)` and subsequent heating from amides. `""underset(underset("or Benzoic acid (A)")("Benzenecarboxylic acid"))(C_(6)H_(5)COOH) underset((ii)Delta)overset((i)Aq.NH_(3))(rarr)underset("Benzamide (B)")(C_(6)H_(5)CONH_(2))`