Aryl chloridesand bromides can be easily prepared by electrophilic substitution of arenes with chlorine and bromine respectively in the presence of Lewis acid catalysts. But why does preparation of aryl iodides requires presence of an oxidizing agent ?

Explanation

Iodination reactions are reversible in nature. To carry out the reaction in the forward direction, the HI formed during the reaction is removed by oxidizing agent such as `HIO_(3)`.