HO–CH₂–CH₂–OH + HIO₄ → 2 HCHO (formaldehyde) + HIO₃ + H₂O

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Explanation (2–3 marks)

• Periodic acid cleaves –CHOH–CHOH (vicinal diol)
• C–C bond breaks
• Each carbon forms a carbonyl compound
• Since both carbons are –CH₂OH → gives 2 molecules of formaldehyde