Question

Which of the following cannot be used for the preparation of iodoform?

• A. Acetone
• B. Methanol
• C. Ethanol
• D. Acetaldehyde

Answer 1

Answer: (B)

Methanol

A compounds containing $C{H}_{3}CO$ or $C{H}_{3}CHOH$ group give positive iodoform test. The formation of iodoform $CH{I}_3$ depends on the previous formation of the $H_{3}C-C=O$ group which next undergoes iodination to $I_{3}C-C=O$ before finally producing $I_{3}CH$. Methanol $C{H}_{3}OH$ does not meet any of this criteria as it does not contain a $H_{3}C-C=O$ group and neither does its oxidation product $HCHO$ methanal.