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JEE Advanced levelSingle correct optionDifficulty 3 of 3g3078

Propanone (1 mol) is treated with benzaldehyde (2 mol) in aqueous ethanolic at room temperature, and both aldol additions go on to dehydration. The product is

  1. A4-Hydroxy-4-phenylbutan-2-one
  2. B4-Phenylbut-3-en-2-one
  3. C1,5-Diphenylpenta-1,4-dien-3-one
  4. D2,4-Diphenylbutan-2-ol

Answer: C

Benzaldehyde has no alpha H, so only propanone forms the enolate. Each of its two groups adds to one , and each aldol loses water to give the conjugated . The 1:1 products (4-hydroxy-4-phenylbutan-2-one and 4-phenylbut-3-en-2-one) are intermediates, not the final product with 2 mol of aldehyde.
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