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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3co233

The keto-aldehyde shown is treated with dilute NaOH and warmed. Which statements are correct?

  1. AThe aldol addition product is a six-membered cyclic beta-hydroxy ketone
  2. BAfter dehydration the product is a conjugated six-membered cyclic enone
  3. CThe aldehyde alpha-enolate attacking the ketone gives a stable five-membered ring
  4. DThe ketone C=O is the electrophile in the productive ring closure

Answer: A, B

The drawn compound is 5-oxohexanal. The ketone methyl enolate attacks the aldehyde carbon, giving a six-membered ring (3-hydroxycyclohexanone) which loses water to give cyclohex-2-enone. The aldehyde alpha-enolate attacking the ketone would make a 4-membered ring, so statements 3 and 4 are wrong.
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