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Explain as to why haloarenes are much less reactive than haloalkenes towards nucleophilic substitution reactions. |
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Answer» Solution :HALOARENES are less reactive than HALOALKANES towards nucleophilic SUBSTITUTION due to the following reasons : (i) Resonance EFFECT : Due to resonance with benzene ring, there is partial double bond character in C-Cl bond. Bond cleave in haloarenes is difficult compared to that in haloalkanes. (II) Difference in hybridisation of carbon atom in C-X bond : Carbon attached to halogen in haloalkanes is `sp^(3)`hybridised while that in haloarene is `sp^(2)`hybridised. `sp^(2)`hybridised carbon is more electronegative because of greater s character, it holds the electrons more tightly, giving less charge to halogen. (iii) It is difficult for electron rich nucleophiles to approach electron rich benzene ring in haloarenes. |
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