Answer: An active methylene compound condenses with an aldehyde.
- A An active methylene compound condenses with an aldehyde
- B A ketone disproportionates into an acid and an alcohol
- C An aldehyde is reduced to the corresponding alcohol by hydride transfer
- D Two ketone molecules condense to form a beta-diketone
Correct answer: A. An active methylene compound condenses with an aldehyde
Explanation: Knoevenagel condensation involves condensation between an aldehyde and an active methylene compound (e.g., malonate).
Curved arrows show the nucleophile attacking the carbonyl carbon while the C=O pi electrons move onto oxygen, giving a tetrahedral alkoxide intermediate.
Concept context
Aldehydes, ketones, carboxylic acids, and their derivatives (esters, amides, acid chlorides). Key reactions include nucleophilic addition, Aldol condensation, Cannizzaro, and Claisen. Very heavily tested in JEE and NEET.
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