(A), (B) and (C ) are three non-cylic funtional isomers of a carbonyl compound with molecular formula `C_(4)H_(8)O`. Isomers (A) and (C ) give positive Tollen's test whereas isomer (B) does not give Tollens' test but gives positive iodoform test. Isomers (A) and (B) on reduction with `Zn(Mg)` | conc. HCl give the same product (D).
(a) Write the structures of (A), (B) ,(C) and (D).
(b) Out of (A), (B) and (C ) isomers, which one is least reactive towards addition of HCN ?

Explanation

(A) and (C) both are aldehydes which give Tollen's test positive but (B) is ketone which does not give Tollen's test positive but gives iodoform test positive .

(b) Out of (A) , (B) and (C) isomers , compound (C) is the least reative towards the addition of HCN.