Ketone identification via selective carbonyl tests

Steps:

• Carbonyls (aldehydes and ketones) form orange precipitates with 2,4-DNPH, confirming X is a carbonyl compound.
• Fehling's reagent oxidizes aldehydes to carboxylic acids (red precipitate), but not ketones.
• No reaction with Fehling's rules out aldehydes, leaving ketones as the only match.
• This pair uniquely proves X is a ketone, excluding alcohols, alkenes, or other functional groups.

Why C is correct:

• Ketones react with 2,4-DNPH (general carbonyl test) but not Fehling's (aldehyde-specific oxidation), per the iodoform and reduction-oxidation distinctions in organic chemistry.

Why the others are wrong:

• A: Iodoform reaction occurs with methyl ketones and some alcohols/aldehydes, not exclusive to ketones.
• B: LiAlH4 reduces many compounds (carbonyls, acids); dichromate oxidizes alcohols and aldehydes, not ketone-specific.
• D: HCN adds to all carbonyls; LiAlH4 reduces various groups, failing to distinguish ketones.

Final answer: C