Question

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

Hint:

Avoid oxidizing acids like \( H_2SO_4 \) when using iodide ions — they reduce reaction efficiency by forming iodine.

Answer 1

Step 1: In the reaction of alcohols with KI, HI is required as a nucleophile to replace the hydroxyl group.
Step 2: When sulphuric acid (H\(_2\)SO\(_4\)) is used, it oxidizes iodide ions (\( I^- \)) to iodine (\( I_2 \)), reducing the amount of HI available for the reaction.
Step 3: Hence, sulphuric acid is avoided, and phosphoric acid (H\(_3\)PO\(_4\)) is preferred instead, as it does not oxidize iodide.