Question

why direct iodination of benzene is difficult

Answer 1

Iodination of benzene is difficult bcoz they require presence of oxidizing agents such as HNO3,HIO4 to oxidize HI. Aryl chlorides( halogens bonded with sp^3 hybridised)and bromides can be easily prepared by electrophilic substitution with cl,br at dark ordinary temperature in presence of Lewis acid as catalyst to generate electrophile but in case of iodine the reactions are reversible

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Answer 2

Iodination of benzene is difficult bcoz they require presence of oxidizing agents such as HNO3,HIO4 to oxidize HI. Aryl chlorides( halogens bonded with sp^3 hybridised)and bromides can be easily prepared by electrophilic substitution with cl,br at dark ordinary temperature in presence of Lewis acid as catalyst to generate electrophile but in case of iodine the reactions are reversible