The correct order of increasing reactivity of $\mathrm{C} \mathrm{X}$ bond towards nucleophile in the…
The correct order of increasing reactivity of $\mathrm{C} \mathrm{X}$ bond towards nucleophile in the following compounds is
$I < II < IV < III$
$II < III < I < IV$
IV $< $ III $< $ I $< $ II
III $ < $ II $ < $ I $ < $ IV
Solution
Key Idea Alkyl halides are more reactive towards nucleophilic substitution. Reactivity depends upon the stability of carbocation intermediate formed.
Among the given halides, aryl halide $\left(\mathrm{C}_6 \mathrm{H}_5 \mathrm{X}\right)$ is least reactive towards nucleophile as in it the $\mathrm{C}-\mathrm{X}$ bond acquire some double bond character due to resonance. Presence of electron withdrawing groups like $-\mathrm{NO}_2$ at ortho and para positions facilitate the nucleophilic displacenent of $-\mathrm{X}$ of aryl halide. Among alkyl halides, $3^{\circ}$ halides are more reactive as compared to $2^{\circ}$ halides due to the formation of more stable carbocation. Hence, the order of reactivity of $\mathrm{C}-\mathrm{X}$ bond towards nucleophile is as
