NEET 2026, Chemistry Q18: Properties and Important Reactions of Aldehydes & Ketones

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Compound P(C $_{8}$ H $_{8}$ O) gives a red orange precipitate with 2,4-DNP reagent and it does not reduce Fehling’s reagent. On drastic oxidation with chromic acid, P gives an aromatic product Q that produces effervescence on treating with aq. NaHCO $_{3}$ . Compound P and Q, respectively, are :

Solution

P (C $_{8}$ H $_{8}$ O) gives a red-orange precipitate with 2,4-DNP, so it contains a carbonyl (>C=O). It does not reduce Fehling’s solution, so it is a ketone, not an aldehyde.

On drastic oxidation, P gives an aromatic acid Q that effervesces with NaHCO $_{3}$ , indicating a –COOH group.

Acetophenone (C $_{6}$ H $_{5}$ –CO–CH $_{3}$ ) fits these criteria: it is a methyl aryl ketone with molecular formula C $_{8}$ H $_{8}$ O, and on strong oxidation it yields benzoic acid (C $_{6}$ H $_{5}$ COOH), which reacts with NaHCO $_{3}$ to liberate CO $_{2}$ .

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NEET 2026, Chemistry Q18: Properties and Important Reactions of Aldehydes & Ketones

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