See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Concept: The conversion of a carbonyl group (C=O) to a methylene group (CH2) — i.e., complete deoxygenation to give a hydrocarbon — requires a specific reaction that removes the oxygen entirely. Step 1: Identify what each reagent does to a carbonyl compound. - (a) H2/Pt: Catalytic hydrogenation reduces a ketone/aldehyde to an alcohol (C=O → CHOH), not to a hydrocarbon (CH2). It does not remove oxygen. - (b) LiAlH4: A strong hydride reducing agent that reduces carbonyls to alcohols (C=O → CHOH). Again, oxygen remains in the product as an alcohol, so this does not give a hydrocarbon. - (c) N2H4-KOH/Δ: This is the Wolff-Kishner reduction. The carbonyl compound first reacts with hydrazine (N2H4) to form a hydrazone (C=NNH2), which upon heating with strong base (KOH) loses N2 and converts C=O directly to CH2. The product is a hydrocarbon — oxygen is completely removed. - (d) K2Cr2O7-H2SO4: This is an oxidizing agent. It would oxidize (not reduce) carbonyl compounds or alcohols further, giving carboxylic acids or other oxidized products. It cannot convert a carbonyl to a hydrocarbon. Step 2: The Wolff-Kishner reduction (N2H4-KOH/Δ) is the classical method specifically designed to convert carbonyl groups (aldehydes and ketones) directly into hydrocarbons (–CH2– or –CH3) by complete removal of the oxygen atom. Step 3: Why other options fail: - H2/Pt and LiAlH4 only reduce to alcohols, retaining oxygen. - K2Cr2O7-H2SO4 is an oxidant, moving in the opposite direction. Only N2H4-KOH/Δ (Wolff-Kishner reduction) achieves full deoxygenation to give a hydrocarbon. Therefore, the correct answer is C.