Aryl chlorides and 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 the preparation of aryl iodides require the presence of an oxidizing agent?

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Solution

Iodination reactions are reversible in nature.
To carry out reaction in forward direction, $H I$ formed during iodination is removed by oxidation. $H I O_{4}$ is used as an oxidizing agent which is used to remove $H I$ .

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Aryl chlorides and 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 the preparation of aryl iodides require the presence of an oxidizing agent?

Iodination reactions are reversible in nature. To carry out reaction in forward direction,HI formed during iodination is removed by oxidation. HIO4 is used as an oxidizing agent which is used to remove HI.

Iodination reactions are reversible in nature.
To carry out reaction in forward direction, $H I$ formed during iodination is removed by oxidation. $H I O_{4}$ is used as an oxidizing agent which is used to remove $H I$ .