JEE Main Chemistry question

A cyclohexane ring bearing an acid chloride substituent (), a ring ketone, and a ring is treated with three successive 1-mole portions of PhMgBr (giving , then , then ), followed by aqueous acidic workup to give . Which of the following statements is correct?

(A)The first mole of PhMgBr reacts at the group, and the by-product is phenol.
(B)The second mole of PhMgBr reacts with the keto group, giving the depicted product .Correct
(C)The second mole of PhMgBr reacts with the acid chloride group, giving the depicted product (with both the acid-chloride- and ketone-derived carbons substituted by phenyl in a single step).
(D)Compound , as depicted (an aryl ketone plus two separate hydroxyls), is the correct final product.

Answer: (B)

Solution

The first equivalent of PhMgBr is consumed instantly in a simple acid–base (proton-transfer) reaction with the molecule's acidic group, generating benzene (not phenol) as the by-product and a magnesium alkoxide at that position, leaving the ring ketone and the acid chloride untouched — so the claim in (A) that

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Question ID VK-148148