Chemistry - Halogen Derivative Question with Solution | TestHub

Arrange the following compounds in order of their reactivity towards${\mathrm{S}}_{\mathrm{N}}2$reaction
$\left(\mathrm{i}\right)$$\mathrm{C}{\mathrm{H}}_3(\mathrm{C}{\mathrm{H}}_2{)}_3\mathrm{C}{\mathrm{H}}_2\mathrm{B}\mathrm{r}$
$\left(\mathrm{i}\mathrm{i}\right)$$(\mathrm{C}{\mathrm{H}}_3{)}_2\mathrm{C}\mathrm{H}\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\mathrm{B}\mathrm{r}$
$\begin{array}{l}{\text{CH}}_{\text{3}}\\ \text{|}\\ \left(\text{iii}\right){\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}-\text{CH}-{\text{CH}}_{\text{2}}\text{Br}\end{array}$
$\begin{array}{l}{\text{CH}}_{\text{3}}\\ \text{|}\\ \left(\text{iv}\right){\text{CH}}_{\text{3}}-\text{C}-{\text{CH}}_{\text{2}}\text{Br}\\ \text{|}\\ {\text{CH}}_{\text{3}}\end{array}$