Question

The increasing order of the reactivity of the following halides for the $S_{N}1$ reaction is :
$C{H}_3\underset{Cl}{\underset{|}{C}}HC{H}_{2}C{H}_3$ $C{H}_{3}C{H}_{2}C{H}_{2}Cl$ $p-H_{3}CO-C_6{H}_4-C{H}_{2}Cl$
(I) (II) (III)

• A. $\left(II\right)<\left(I\right)<\left(III\right)$
• B. $\left(I\right)<\left(III\right)<\left(II\right)$
• C. $\left(II\right)<\left(III\right)<\left(I\right)$
• D. $\left(III\right)<\left(II\right)<\left(I\right)$

Answer 1

The correct option is A $\left(II\right)<\left(I\right)<\left(III\right)$

The increasing order of the reactivity of the halides for the SN1 reaction is $\left(II\right)<\left(I\right)<\left(III\right)$.
$\left(II\right)$ is primary alkyl halide.
$\left(I\right)$ is secondary alkyl halide.
Primary alkyl halide is less reactive towards SN1 reaction than secondary alkyl halide.
In $\left(III\right)$, the carbocation generated is stabilised due to resonance. Hence, $\left(III\right)$ is most reactive towards SN1 reaction.