See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

Concept: The starting material is cyclohexyl methyl ketone (a ketone with a methyl group). The product is cyclohexane bearing a -CH(CH3)CH2CH2CH3 group, meaning the carbonyl oxygen has been completely removed and replaced by two carbons (one CH3 already present, one new CH2CH2CH3 chain added) with a C-H bond at the former carbonyl carbon. This is a net replacement of C=O with C-H plus extension of the carbon chain, which is characteristic of a Wittig reaction followed by reduction. Step 1 - Wittig reaction: Using the ylide (C6H5)3P=CHCH2CH3 (a stabilized or semi-stabilized ylide with a propyl chain), the Wittig reaction with cyclohexyl methyl ketone converts the C=O into C=C, giving the alkene: cyclohexyl-C(CH3)=CHCH2CH3. This installs the new carbon chain and eliminates oxygen. Step 2 - Hydroboration-oxidation or reduction: B2H6 (diborane) followed by CH3CO2H (acetic acid as a proton source for workup) reduces the resulting alkene via hydroboration. Hydroboration of the trisubstituted alkene cyclohexyl-C(CH3)=CHCH2CH3 with B2H6 gives an organoborane, and protonolysis with CH3CO2H (a proton source that cleaves the C-B bond) gives the reduced alkane: cyclohexyl-CH(CH3)CH2CH2CH3. This matches the product exactly. Why other options fail: (a) Grignard addition of CH3CH2CH2MgBr to the ketone gives a tertiary alcohol after H3O+ workup. PCC oxidizes secondary/primary alcohols but cannot oxidize a tertiary alcohol, so no further conversion occurs. Product would be a tertiary alcohol, not the desired alkane. (b) Same Grignard gives tertiary alcohol; H2SO4/heat causes dehydration to an alkene, then PCC cannot oxidize a simple alkene to the desired product. This does not give the target molecule. (d) Wittig with (C6H5)3P=CHCH2CH3 alone gives the alkene, but H2O alone cannot reduce the double bond. The alkene would not be converted to the saturated product without a reducing agent. Option (c) uses the Wittig reagent to form the alkene intermediate and then uses B2H6 / CH3CO2H to effect hydroboration followed by protonolysis, delivering the correct saturated product cyclohexyl-CH(CH3)CH2CH2CH3. Therefore, the correct answer is C.