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Aryl chlorides and bromides can be easil...

Aryl chlorides and bromides can be easily prepared by electrophilic substitution of arenas with chlorine and bromine respectively in the presence of Lewis acid catalyst. But why does preparation of aryl iodides requires presence of an oxidising agent?

Text Solution

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Iodination reactions are reversible in nature. Therefore, to carry out the reaction in the forward direction, HI formed during iodination is removed by oxidation with iodic acid `(HIO_(3))` or nitric acid (`HNO_(3)`).

`5HI+HIO_(3) to 3I_(2)+3H_(2)O`
`2HI+2HNO_(3) to I_(2)+2H_(2)O+2NO_(2)`
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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 preparation of aryl iodides requires presence of an oxidising agent ?

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 preparation of aryl iodides require presence of an oxidising agent?

Knowledge Check

  • Arenes when treated with chlorine or bromine in the presence of Lewis acid as a catalyst undergo___________reaction.

    A
    Nucleophilic substitution
    B
    electrophilic substitution
    C
    rearrangement
    D
    dehydrohalogenation

  • Assertion: Aryl iodides can be prepared by reaction of arenes with iodine in the presence of an oxidising agent. Reason: Oxidising agent oxidises I_(2) into HI.

    A
    Assertion and reason both are correct and reason is correct explanaion of assertion.
    B
    Assertion and reason both are wrong statements.
    C
    Assertion is correct but reason is wrong statement.
    D
    Assertion is wrong but reason is correct statement.

  • Assertion: Aryl iodides can be prepared by reaction of arenes with iodine in the presence of an oxidising agent. Reason: Oxidising agent oxidises I_(2) into HI.

    A
    Assertion and reason both are correct and reason is correct explanation of assertion.
    B
    Assertion and reason both are wrong statements.
    C
    Assertion is correct but reason is wrong statement.
    D
    Assertion is wrong but reason is correct statement.

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