Answer:
Haloarenes are much less reactive than haloalkanes towardsreactions
due to the following reasons
(i) Resonance effect (C?Cl) bond is stabilised due to
resonance. This resonance arises as a result of delocalisation of lone pair on Cl
atoms and -elctrons
in benzene sextet. (C?Cl) bond acquires partial double bond character.
(ii)
Electronegativity of sp2 > sp3
(C?Cl) bond length in aryl halide < alkyi halide Bond energy (C?Cl) > alkyi
halide, Thus, sn reaction is not
feasible in aryl halide.
(iii) If reaction
takes place, phenyl carbocation isvery less stable than alkyl
carbocation.
(iv) Nucleophile is repelled by electron rich aryl halide.
Or
(i) For reaction
[1]
being
larger in size causes steric hindrance for nucleophilic attack.
(ii)
Due to the presence of three alky] groups in (A), nucleophile
cannot approach central carbon in reaction.
Thus, reaction
is faster in (6).
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