The increasing order of the rate of `HCN` addition of compound a-d is
(i) `HCHO`
(ii) `CH_(3)COCH_(3)`
(iii) `PhCOCH_(3)`
(iv) `PhCOPh`

Options

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

Answer

C

Explanation

Is the correct order. It is based on steric hindrance. More the hindrance, lesser will be the reactivity.