The increasing order of the rate of HCN addition to compound A-D is
(A) HCHO
(B) `CH_(3)COOH_(3)`
( C) `PhCOCH_(3)`
(D) `PhCOPh`

Options

A. `D lt C lt B lt A`
B. `C lt D lt B lt A`
C. `A lt B lt C lt D`
D. `D lt B lt C lt A`

Answer

A

Explanation

Addition of HCN to carbonyl compounds is nucleophilic addition reaction. The order of reactivity of carbonyl compound is
`HCHO gt CH_(3)COCH_(3) gt Ph. COCH_(3)gt Ph COPh`
The lower reactivity of Ketones is due to presence of two alkyl groups which show `+I` effect. The reactivity of ketones decreases as the size of alkyl group increases.