The halogen atom’s –I effect and deactivating influence, along with resonance, make the benzene ring in haloarenes somewhat deactivated compared to benzene. As a result, electrophilic substitution reactions in haloarenes occur more slowly and require more drastic conditions than those in benzene.
Why do electrophilic substitution reactions in haloarenes occur more slowly and under harsher conditions compared to benzene?
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Electrophilic substitution reactions in haloarenes occur more slowly and under harsher conditions compared to benzene due to the deactivating influence of the halogen substituent. The electronegative halogen withdraws electron density from the benzene ring, reducing its nucleophilic nature and making it less reactive towards electrophiles. The electron-withdrawing effect of the halogen also weakens the aromatic ring’s nucleophilic attack on electrophiles. As a result, higher temperatures and more aggressive reaction conditions, such as the use of Lewis acid catalysts, are often required to overcome the deactivating influence of the halogen and facilitate electrophilic substitution on the aromatic ring in haloarenes.