See image — Reaction Mechanism Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the substrate: The starting material is a 1,2-disubstituted cyclohexane. C1 bears a methyl group and a tertiary ester (-C(=O)OCH3) directly on the ring carbon. C2 bears a -CH2-C(=O)OCH3 group (an acetate-type ester via a methylene spacer). Step 2 - Reactivity of the two esters toward PhMgBr (1 equiv): Grignard reagents react with esters, but the rate and accessibility depend on steric and electronic factors. The ester at C1 is a tertiary ester (the carbonyl carbon is attached to a quaternary carbon bearing CH3 and the ring), making it highly sterically hindered. The ester in the -CH2-C(=O)OCH3 group is a primary/secondary ester (the carbonyl is on the end of a methylene chain), making it far less sterically hindered and more accessible to nucleophilic attack. Step 3 - Selectivity with 1 equivalent of PhMgBr: Because only 1 equivalent of PhMgBr is used, it selectively reacts with the less hindered ester. The -CH2-C(=O)OCH3 ester reacts with PhMgBr. Normally, a Grignard adds twice to an ester (giving a tertiary alcohol), but with a sterically demanding Grignard like PhMgBr and careful control, the first addition gives a ketone intermediate (after loss of -OCH3), and the ketone can be less reactive or the second equivalent is not available. However, in practice with 1 equiv PhMgBr reacting with the less hindered ester -CH2COOCH3, the product after workup is the ketone -CH2-C(=O)-Ph (because the tetrahedral intermediate collapses by expelling methoxide to give the ketone, and no second equivalent is present to add again). Step 4 - Result: The C1 tertiary ester (-C(=O)OCH3) remains unreacted due to steric hindrance. The -CH2-C(=O)OCH3 is converted to -CH2-C(=O)-Ph. This matches option (d): cyclohexane ring with CH3 and C(=O)OCH3 at C1 (unchanged), and CH2-C(=O)-Ph at C2. Step 5 - Why other options fail: - (a) and (b): These show reaction at the hindered C1 tertiary ester, which is disfavored sterically. Also the ring is not shown in (a)/(b). - (c): This shows an extra methyl group added to the ring carbon (C2), which would require a different reaction pathway and is not the product of simple ester + PhMgBr. Therefore, the correct answer is D.