Which synthetic reduction method is most appropriate for converting an acid-sensitive carbonyl compound containing an acetal functional group into an alkane?

Answer and explanation

Correct answer: A. Wolff-Kishner reduction (NH2NH2 / KOH in ethylene glycol, heat)

  1. Step 1: To reduce a carbonyl group () to a methylene group (), two primary methods exist: Clemmensen reduction and Wolff-Kishner reduction.
  2. Step 2: Clemmensen reduction uses strongly acidic conditions (), which would rapidly hydrolyze and destroy acid-sensitive groups like acetals, ethers, or esters.
  3. Step 3: Wolff-Kishner reduction employs strongly basic conditions (hydrazine followed by in high-boiling ethylene glycol at 450–475 K).
  4. Step 4: Because acetals are stable to strong bases, the Wolff-Kishner reduction is the ideal method for acid-sensitive substrates.
Answer
Wolff-Kishner reduction (NH2NH2 / KOH in ethylene glycol, heat)
Why not the others: 'Clemmensen reduction' uses concentrated , which would cleave the acid-sensitive acetal; 'Catalytic hydrogenation with conc. H2SO4' is an aggressive acidic dehydrating condition; 'Sodium borohydride in aqueous acid' reduces carbonyls to alcohols, not alkanes, and decomposes in acid.

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