Why is sulphuric acid not used during the reaction of alcohols with KI?

H₂SO₄ cannot be used along with KI in the conversion of an alcohol to an alkyl iodide as it oxidizes KI in the presence of sulphuric acid (H₂SO₄) to corresponding HI and then to I₂ i.e.,

KI produces HI, In the presence of sulphuric acid (H₂SO₄).
2KI + H₂SO₄ --> 2KHSO₄ +2HI

Since H₂SO₄ is an oxidizing agent, it oxidizes HI( Produced in the reaction to I₂).

2HI + H₂SO₄ --> I₂ +SO₂ +H₂O

As a result, the reaction between alcohol and HI to produce alkyl iodide cannot occur. Therefore, sulphuric acid is not used during the reaction of alcohols with KI. Instead, a non-oxidiznig acid such H₃PO₄ is used.

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