Direct iodination of arenes using is exceptionally difficult because the reaction rapidly achieves an unfavorable equilibrium. Oxidizing agents like or are strictly added to consume the byproduct. If

Question

Direct iodination of arenes using $I_2$ is exceptionally difficult because the reaction rapidly achieves an unfavorable equilibrium. Oxidizing agents like $HIO_4$ or $HNO_3$ are strictly added to consume the $HI$ byproduct. If the $HI$ is deliberately not removed from the system, what specific chemical action does it perform that actively reverses the iodination?

Prashant Kotian · Accepted Answer

Correct answer: B. The direct iodination of benzene () is heavily reversible. Hydrogen iodide () is a powerful reducing agent. In the reverse reaction, it reduces the synthesized aryl iodide, breaking the relatively weak bond to reform the original aromatic hydrocarbon and liberating elemental iodine. To prevent this reductive reversal and drive the reaction forward according to Le Chatelier's principle, an oxidizing agent is added to continuously destroy the as soon as it forms.

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