Question

The order of reactivity of phenyl magnesium bromide $(PhMgBr)$ with the following compounds

• A. III > II > I
• B. II > I > III
• C. I > III > II
• D. I > II > III

Answer 1

Answer: (D)

Since alkyl group has $+I$-effect and aryl group has $+R$-effect, thus greater the number of alkyl and aryl groups attached to the carbonyl group, its reactivity towards nucleophilic addition reaction. Secondly, as the steric crowding on carbonyl group increases, the reactivity decreases accordingly.
$\therefore$ Correct reactivity order for reaction with $PhMgBr$ is