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Question
Chlorobenzene is extremely less reactive towards a nucleophilic substitution reaction. Give two reasons for the same.
Solution
Chlorobenzene is extremely less reactive towards a nucleophilic substitution reaction because of the following reasons:
(1) Resonance effect: The electron pair on chlorine atom is in conjugation with the π - electrons of the benzene ring which results in the following resonance structures:
-
This results in delocalization of the electrons of C − Cl bond and a partial double bond character develops in the bond, which makes it difficult for the nucleophile to cleave the C − Cl bond.
(2) The nucleophile suffers repulsion from the increased electron density on the benzene ring as a result the nucleophile is unable to make a close approach for the attack on the molecule.
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