Chemistry - Halogen Derivative Question with Solution | TestHub

The rate of an ${\text{SN}}^2$ reaction is inversely proportional to the steric hindrance around the carbon atom bearing the leaving group.

The order of reactivity of alkyl halides towards ${\text{SN}}^2$ mechanism is:
Methyl halide $>$ $1^{\circ }$ alkyl halide $>$ $2^{\circ }$ alkyl halide $>$ $3^{\circ }$ alkyl halide.

Among the given options:
${\text{CH}}_3\text{-Br}$ is a methyl halide.
${\text{CH}}_3{\text{-CH}}_2\text{-Br}$ is a $1^{\circ }$ alkyl halide.
$({\text{CH}}_3{)}_2\text{CH-Br}$ is a $2^{\circ }$ alkyl halide.
$({\text{CH}}_3{)}_3\text{C-Br}$ is a $3^{\circ }$ alkyl halide.

Since ${\text{CH}}_3\text{-Br}$ has the least steric hindrance, it is hydrolyzed most rapidly by the ${\text{SN}}^2$ mechanism.

Answer: ${\text{CH}}_3\text{-Br}$