Which of the following reactions is used to **distinguish** acetophenone (PhCOCH₃) from benzaldehyde (PhCHO)?
ANeither gives any test
BBoth give positive iodoform test
CAcetophenone gives positive iodoform test (CH₃-CO- present); benzaldehyde does NOT (no CH₃-CO-). Conversely, benzaldehyde gives positive Tollens' (silver mirror); acetophenone does NOT
DBoth decolourise Br₂ in CCl₄
Answer & Solution
Correct answer: C. Acetophenone gives positive iodoform test (CH₃-CO- present); benzaldehyde does NOT (no CH₃-CO-). Conversely, benzaldehyde gives positive Tollens' (silver mirror); acetophenone does NOT
**Acetophenone (PhCOCH₃)**: methyl ketone → **positive iodoform (CHI₃ yellow ppt)**; ketone → **negative Tollens'**. **Benzaldehyde (PhCHO)**: not a methyl ketone → **negative iodoform**; is an aldehyde → **positive Tollens' (silver mirror)**. Used together, these two tests cleanly distinguish them. **Fehling's is negative for both** (aromatic).
Related questions
Cannizzaro reaction happens with aldehydes that have no:Aldol condensation needs the molecule to carry at least one:A positive iodoform test shows the compound is a methyl:Adding water to alkynes other than ethyne gives:Adding water to ethyne gives which product?Reduction of a carbonyl group using glycol is named after:Zinc amalgam with concentrated hydrochloric acid gives the reduction of:Acyl chloride hydrogenated over palladium on barium sulphate gives the: