Q.
The correct order of increasing reactivity of $C- X$ bond towards nucleophile in the following compounds is
AIPMTAIPMT 2010Haloalkanes and Haloarenes
Solution:
Alkyl halides are more reactive towards nucleophilic substitution. Reactivity depends upon the stability of carbocation intermediate formed.
Among the given halides, aryl halide ($C_6H_5X$) is least reactive towards nucleophile due to the possible four reason
(i) Reasonance effect
(ii) Hybridisation
(iii) Unstability of phenyl cation
(iv) Double bond character
$C - X$ bond acquire some double bond character due to resonance. Presence of electron withdrawing groups like - $NO_2$ at ortho and para-positions facilitate the nucleophilic displacement of $-X$ 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 $C - X$ bond towards nucleophile is as
