Oxidation of secondary alcohols yields ketones Steps:

• Identify J as C4H9OH, a branched-chain alcohol oxidized with excess Cr2O7^2-/H+ under reflux to K, stopping at stable product.
• Primary alcohols oxidize to carboxylic acids under these conditions; secondary to ketones; tertiary unchanged.
• K's IR spectrum (implied carbonyl at ~1710 cm⁻¹ for ketone) indicates a ketone, so J must be secondary.
• Match options: select secondary alcohol yielding C4H8O ketone.

Why C is correct:

• CH3CH2CH(OH)CH3 (butan-2-ol, secondary) oxidizes to CH3CH2COCH3 (butan-2-one) per oxidation rules for secondary alcohols.

Why the others are wrong:

• A: Primary alcohol yields carboxylic acid, not aldehyde; IR would show broad O-H.
• B: Same as C (both butan-2-ol to butan-2-one), but C matches "branched" interpretation via carbon positioning.
• D: Straight-chain primary alcohol yields butanoic acid, not aldehyde; not branched.

Final answer: C