See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Step 1 - Identify functional group clues: - Forms a 2,4-DNP derivative: indicates a carbonyl group (aldehyde or ketone). - Reduces Tollen's reagent: indicates an aldehyde (not a ketone). - Undergoes Cannizzaro reaction: indicates an aldehyde with no alpha-hydrogen (so the CHO group must be attached directly to the benzene ring, i.e., an aryl aldehyde, which has no alpha-H). Step 2 - Determine the molecular formula requirement: C9H10O with an aldehyde group (CHO). The benzaldehyde core is C7H6O (C6H5CHO). We need C9H10O, so we need two extra carbons and four extra hydrogens beyond benzaldehyde: C7H6O + C2H4 = C9H10O. An ethyl group (C2H5) adds C2H5, but we also lose one H from the ring, net addition is C2H4. So the compound is ethylbenzaldehyde. Step 3 - Determine the substitution pattern using oxidation product: - Vigorous oxidation gives 1,2-benzenedicarboxylic acid (phthalic acid), which means both substituents (CHO and ethyl) are on adjacent (ortho) positions on the benzene ring. - The CHO oxidizes to COOH and the ethyl group oxidizes to COOH, giving a 1,2-dicarboxylic acid (phthalic acid) only if both substituents are ortho to each other. Step 4 - Match to options: - Option (b) shows 2-ethylbenzaldehyde: ethyl group and CHO group both at ortho positions on the benzene ring. This gives 1,2-benzenedicarboxylic acid upon vigorous oxidation. It is an aryl aldehyde (no alpha-H, satisfying Cannizzaro), reduces Tollen's reagent, and forms 2,4-DNP derivative. Step 5 - Why other options fail: - Option (a): para-substituted, would give 1,4-benzenedicarboxylic acid (terephthalic acid), not 1,2. - Option (c): contains a ketone group (COCH3) in addition to CHO; the ketone would not reduce Tollen's reagent (only the aldehyde would), and the molecular formula may differ; also the Cannizzaro condition is satisfied but the oxidation product pattern differs. - Option (d): meta-substituted, would give 1,3-benzenedicarboxylic acid (isophthalic acid), not 1,2. Therefore, the correct answer is B.