JEE Main levelSingle correct optionDifficulty 2 of 3o4138
Assertion (A): A beta-hydroxy ketone loses water readily with dilute alkali even though OHX− is a poor leaving group.
Reason (R): The enolate formed first is a stabilised carbanion that expels OHX− to give a conjugated enone.
ABoth A and R are true, but R is not the correct explanation of A.
BBoth A and R are true, and R is the correct explanation of A.
CA is true, but R is false.
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 OHX−. The conjugated enone product provides the driving force. R explains why a poor leaving group is acceptable.