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JEE Main levelSingle correct optionDifficulty 2 of 3o4138

Assertion (A): A beta-hydroxy ketone loses water readily with dilute alkali even though is a poor leaving group. Reason (R): The enolate formed first is a stabilised carbanion that expels to give a conjugated enone.

  1. ABoth A and R are true, but R is not the correct explanation of A.
  2. BBoth A and R are true, and R is the correct explanation of A.
  3. CA is true, but R is false.
  4. DA is false, but R is true.

Answer: B

This is an E1cB dehydration. Base removes the acidic alpha-H, giving an enolate, and the negative charge pushes out . The conjugated enone product provides the driving force. R explains why a poor leaving group is acceptable.
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