An aromatic aldehyde (A) of molecular formula `C_(7)H_(6)O` which has the smell of bitter almonds on treatment with `(CH_(3)CO)_(2)OandCH_(3)COONa` to give compound (B) which is an aromatic unsaturated of acid. (A) also reacts with (A) in the presence of alc. KCN to give dimer (C). Identify (A), (B) and (C). Explain the reactions.

Explanation

(i) An organic compound which has the smell of bitter almonds is benzaldehyde `C_(6)H_(5)CHO` and it is (A).
(ii) Benzaldehyde reacts with acetic anhydride in the presence of sodium acetate gives Cinnamic acid.
`underset((A))(C_(6)H_(5)CHO)+(CH_(3)CO)_(2)Ooverset(CH_(3)COONa)tounderset((B))(C_(6)H_(5)CH=CHCOOH)+CH_(3)COOH`
(iii) Benzaldehyde on treatment with alcoholic KCN gives Benzoin a dimer and it is (C).
`C_(6)H_(5)CHO+C_(6)H_(5)CHOoverset("Alcoholic" KCN)tounderset((C))(C_(6)H_(5)-underset(OH)underset(|)(CH)-underset(O)underset(||)(C)-C_(6)H_(5))`