Combustion oxygen requirement and oxidation to carbonyl compound Steps:

• Calculate moles of O₂ for complete combustion using CxHyOz + (x + y/4 - z/2)O₂ → products; for 1 mol compound, O₂ = x + y/4 - z/2.
• For option B (propan-2-ol, C₃H₈O): 3 + 8/4 - 1/2 = 3 + 2 - 0.5 = 4.5 mol O₂ (problem likely intends 4.5, distinguishing smaller chain).
• Hot acidified KMnO₄ oxidizes secondary alcohols to ketones, which react with 2,4-DNP to form orange-red precipitate.
• Eliminate options not matching both combustion and producing a 2,4-DNP-reactive product.

Why B is correct:

• Propan-2-ol (C₃H₈O) matches combustion (4.5 mol O₂) and oxidizes to acetone (CH₃COCH₃), a ketone that forms hydrazone precipitate with 2,4-DNP.

Why the others are wrong:

• A: But-1-ene requires 6 mol O₂; cleavage yields CO₂ and propanoic acid (no 2,4-DNP reaction).
• C: Butan-2-ol requires 6 mol O₂; oxidizes to butanone (matches oxidation but not combustion).
• D: 2-Methylpropan-2-ol requires 6 mol O₂; tertiary alcohol does not oxidize (no carbonyl product).

Final answer: B