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JEE Advanced 2024 Paper 1 · Chemistry · Carbonyl Compounds, Carboxylic Acids and Amines · medium

Match each reaction of benzaldehyde in List-I with the organic product(s) in List-II. PhCHO heated with (CH3CO)2O and anhydrous CH3COONa, then…

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Match each reaction of benzaldehyde in List-I with the organic product(s) in List-II.

| List-I | List-II |
|---|---|
| P. PhCHO\mathrm{PhCHO} heated with (CH3CO)2O(\mathrm{CH_3CO})_2\mathrm{O} and anhydrous CH3COONa\mathrm{CH_3COONa}, then acidified | 1. Cinnamaldehyde |
| Q. PhCHO\mathrm{PhCHO} with KCN\mathrm{KCN} in aqueous ethanol | 2. Benzoin |
| R. PhCHO\mathrm{PhCHO} with CH3CHO\mathrm{CH_3CHO}, dilute NaOH, then heat | 3. Benzyl alcohol and benzoate (both) |
| S. PhCHO\mathrm{PhCHO} with concentrated NaOH | 4. Cinnamic acid |
| | 5. Mandelic acid |
  1. A. P→4, Q→2, R→1, S→3
  2. B. P→4, Q→5, R→1, S→3
  3. C. P→1, Q→2, R→4, S→3
  4. D. P→4, Q→2, R→3, S→1
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Answer: (A) P→4, Q→2, R→1, S→3

P: Perkin reaction, the anhydride enolate adds to benzaldehyde and dehydration gives PhCH=CHCOOH\mathrm{PhCH{=}CHCOOH}, cinnamic acid: 4. Q: cyanide-catalysed benzoin condensation, PhCH(OH)COPh\mathrm{PhCH(OH)COPh}, benzoin: 2. R: crossed aldol (Claisen–Schmidt) condensation in which only acetaldehyde has α\alpha-hydrogens, giving PhCH=CHCHO\mathrm{PhCH{=}CHCHO}, cinnamaldehyde, after dehydration: 1. S: benzaldehyde has no α\alpha-hydrogen so conc. NaOH causes Cannizzaro disproportionation to benzyl alcohol and sodium benzoate: 3. Mandelic acid would need the cyanohydrin followed by hydrolysis, which is not formed under the KCN conditions of Q. The only fully correct code is P→4, Q→2, R→1, S→3.
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