See image — Reaction Mechanism Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the reagents: Ethyl acetate (CH3CO2Et) reacts with a bifunctional Grignard reagent (CH2)5(MgBr)2, which is 1,5-bis(bromomagnesio)pentane, i.e., BrMg-(CH2)5-MgBr. The reaction is followed by acid workup (H+). Step 2 - Understand the reaction mechanism: A bifunctional Grignard reagent reacting with an ester undergoes double intramolecular addition. The first end of the Grignard (one MgBr end) attacks the carbonyl of the ester (CH3CO2Et), displacing ethoxide to form a ketone intermediate (after the first addition and loss of OEt-). Then the second MgBr end of the same molecule attacks the newly formed ketone intramolecularly. Step 3 - Trace the carbon skeleton: The ester CH3CO2Et contributes a CH3-C(=O)- fragment (2 carbons). The bifunctional Grignard BrMg-(CH2)5-MgBr contributes 5 carbons. Total carbons: 2 + 5 = 7. The product has molecular formula C7H14O, consistent. Step 4 - Determine the product structure: The first Grignard end attacks the ester carbonyl, releases EtO-, giving a ketone: CH3-C(=O)-(CH2)5-MgBr. Then intramolecular attack of the second MgBr end on the ketone carbonyl forms a 5-membered ring transition state... actually counting: the ketone carbon + 5 CH2 groups + the attacking carbon forms a ring. The ketone is at position 1 (with CH3), and the chain -(CH2)5- connects back, making a 6-membered carbocyclic ring (1 carbonyl carbon + 5 methylene carbons = 6-membered ring), and upon acid workup gives a tertiary alcohol. The CH3 group and OH are both on the same carbon (C1 of cyclohexane), giving 1-methylcyclohexan-1-ol. Step 5 - Verify molecular formula: 1-methylcyclohexan-1-ol: C7H14O. Cyclohexane ring (6C) + 1 methyl (1C) = 7C; ring has 10H + methyl 3H + OH = 14H + O. Formula C7H14O. Correct. Step 6 - Why other options fail: - (a) 1-methyl-2-cyclohexanol: C7H14O but wrong connectivity; this would require different regiochemistry not produced here. - (c) heptan-2-one: This is a ketone (no OH), not consistent with Grignard addition followed by acid workup giving an alcohol. - (d) cyclohexanemethanol: C7H14O but this is a primary alcohol with formula C7H14O only if cyclohexyl-CH2OH = C7H14O: cyclohexyl (6C) + CH2OH (1C) = C7H14O. This would require a different reaction pathway and does not arise from this intramolecular cyclization. The intramolecular double Grignard addition to ethyl acetate with BrMg(CH2)5MgBr gives 1-methylcyclohexan-1-ol, which matches option (b). Therefore, the correct answer is B.