Which of the following alkyl halides undergoes hydrolysis with aqueous `KOH` at the fastest rate ?

Options

A. `CH_(3)overset(Cl)overset(|)(CH)CH_(3)`
B. `(CH_(3))_(2)CHCH_(2)Cl`
C. `CH_(3)CH_(2)CH_(2)Cl`
D. `CH_(3)CH_(2)Br`

Answer

D

Explanation

All are primary halides undergoing `S_(N)1` mechanism . During hydrolysis (a nucleophilic displacement) , the `C-X` bond is broken in the rate controlling step. Thus the order of reactivity (which depends upon the strength of `C-X` bond) is
`R-I gt R - Br gt R - Cl gt R - F`