Same chapter3 marksDifficulty: Medium
How would you distinguish between an aldehyde and a ketone in the laboratory?
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3 marksDifficulty: Medium
Describe the aldol condensation and the Cannizzaro reaction, and say which aldehydes undergo each.
Original Khojo Papers practice question — not from a past board paper.
Answer
The aldol condensation occurs with aldehydes and ketones that have at least one alpha hydrogen: in dilute alkali two molecules combine to give a beta-hydroxy carbonyl compound, which may lose water. The Cannizzaro reaction occurs with aldehydes that have no alpha hydrogen: in concentrated alkali one molecule is oxidised to the acid salt and another reduced to the alcohol.
No citable source has been recorded for this record. Treat it as practice material, not as fact.
Explanation
Formaldehyde and benzaldehyde undergo the Cannizzaro reaction; acetaldehyde undergoes the aldol condensation.
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