See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

Step 1 - Identify reagent A: The starting material is an alpha,beta-unsaturated ester (acrylate derivative): cyclohexylidene-CH=CH group with -CO2Et. The product after reagent A is the corresponding allylic alcohol: -CH2-OH, with the double bond retained. To convert an ester (-CO2Et) to a primary alcohol (-CH2-OH) while preserving the carbon-carbon double bond, we need LiAlH4. NaBH4 is a milder reducing agent that selectively reduces ketones/aldehydes but does NOT efficiently reduce esters under normal conditions. LiAlH4 reduces esters to primary alcohols. Therefore, A = LiAlH4. Step 2 - Identify product B: The allylic alcohol (cyclohexane ring with exocyclic =CH-CH2-OH) is treated with MnO2. MnO2 is a selective oxidant that oxidizes allylic and benzylic alcohols to the corresponding carbonyl compounds. An allylic primary alcohol (-CH2-OH adjacent to a C=C) is oxidized by MnO2 to an allylic aldehyde (-CHO). The double bond is preserved. Therefore, B = cyclohexane ring with exocyclic double bond CH= and substituent -CHO (aldehyde). Step 3 - Why other options fail: (a) and (b) use NaBH4, which cannot reduce esters to alcohols efficiently, so A cannot be NaBH4. (d) uses LiAlH4 correctly but gives -CO2H as B, which is incorrect because MnO2 oxidizes primary allylic alcohols to aldehydes, not carboxylic acids. (c) correctly identifies A = LiAlH4 and B = the allylic aldehyde (-CHO). Therefore, the correct answer is C.