Which one of the following compounds will provide a tertiary alcohol on reaction with excess of CH3MgBr followed by hydrolysis?
(A)(see structure)
(B)(see structure)
(C)(see structure)✓ Correct
(D)(see structure)
Answer: (C)
Solution
A Grignard reagent attacks an ester twice: the first addition expels the alkoxide and leaves a ketone, and the second adds to that ketone, so hydrolysis delivers an alcohol carrying two alkyl groups from the reagent. Phenyl acetate, CH3COOC6H5, therefore picks up two methyl groups at the acetyl carbon and gives 2-methylpropan-2-ol. A nitrile, by contrast, adds the reagent once and stops at a ketone on hydrolysis, so it cannot reach a tertiary alcohol. The compound that provides a tertiary alcohol is the ester phenyl acetate, the product being 2-methylpropan-2-ol.
JEE Main · 2021 · 22 Jul 2021 · Shift 2 · Single correct option