why are arylhalide less reactive than alkyl halide in nucleophilic substitution reaction?

Asked by medha_sharma | 30th Nov, 2014, 10:20: AM

Expert Answer:

Dear shankerabhi@yahoo.co.in

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The carbon-chlorine bond in chlorobenzene is stronger than expected. There is an interaction between one of the lone pairs on the chlorine atom and the delocalised ring electrons, and this strengthens the bond. Hence there is an extra strength of the carbon-halogen bond in aryl halides.
Both Sn1 and SN2 mechanisms involve breaking the carbon-halogen bond at some stage. It is difficult to break this bond. Hence, nucleophillic reactions are difficult in aryl halides. This is not the case in alkyl halides.

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Answered by Prachi Sawant | 1st Dec, 2014, 12:43: PM