Chemistry - GOC Question with Solution | TestHub

Electron Releasing Group favours${\text{S}}_{\text{N}}\text{1}$reactivity with$\text{HBr}$.$\text{EWG}$retards${\text{S}}_{\text{N}}\text{1}$reactivity with$\text{HBr}$.
$\text{ERG}$effect of$\left(-\mathrm{O}\mathrm{M}\mathrm{e}\right)(+\mathrm{R},\mathrm{}-\mathrm{I})$is greater than$\left(\mathrm{M}\mathrm{e}\right)$group$\left(+\mathrm{I }\mathrm{}\mathrm{a}\mathrm{n}\mathrm{d }\mathrm{}\mathrm{H}.\mathrm{C}.\right).$So, reactivity of$\mathrm{I}\mathrm{I}\mathrm{I}>\mathrm{I}\mathrm{I}.\mathrm{}$
In$\left(\mathrm{I}\mathrm{V}\right),\mathrm{}\left(-\mathrm{O}\mathrm{M}\mathrm{e}\right)$group is at m-position and exerts only$-\mathrm{I}$effect and so reactivity of$\left(\mathrm{I}\mathrm{V}\right)$is less than$\left(\mathrm{I}\right).$
So the reactivity order is:$\mathrm{I}\mathrm{I}\mathrm{I}>\mathrm{I}\mathrm{I}>\mathrm{I}>\mathrm{I}\mathrm{V}$