Match List I with List II
| List I | List II |
| A. Reimer-Tiemann reaction | I. Benzene |
| B. Kolbe's reaction | II. Picric acid |
| C. Nitration of phenol with conc. \(HNO_3\) | III. Salicylic acid |
| D. Reaction of phenol with Zn dust | IV. Salicylaldehyde |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A-IV, B-III, C-II, D-I
Phenol has an –OH group that activates the ring towards electrophilic substitution at the ortho and para positions; in alkali the phenoxide ion is even more reactive. Reimer-Tiemann and Kolbe’s reactions put a –CHO or –COOH group at the ortho position, nitration puts in –\( \ce{NO2} \) groups, and zinc dust removes the –OH group altogether.
A. Reimer-Tiemann reaction — This matches IV. Salicylaldehyde. Phenol with chloroform in aqueous NaOH introduces a –CHO group at the ortho position; the substituted benzal chloride formed is hydrolysed by the alkali and acidification gives salicylaldehyde.
\( \displaystyle \ce{C6H5OH} \xrightarrow[\text{(ii) }\ce{H+}]{\text{(i) }\ce{CHCl3}\text{, aq. }\ce{NaOH}} \ce{\mathit{o}-HOC6H4CHO} \)
B. Kolbe’s reaction — This matches III. Salicylic acid. Sodium phenoxide reacts with carbon dioxide, a weak electrophile, and acidification gives ortho-hydroxybenzoic acid.
\( \displaystyle \ce{C6H5ONa} \xrightarrow[\text{(ii) }\ce{H+}]{\text{(i) }\ce{CO2}} \ce{\mathit{o}-HOC6H4COOH} \)
C. Nitration of phenol with conc. HNO3 — This matches II. Picric acid. Concentrated nitric acid nitrates all three activated positions, giving 2,4,6-trinitrophenol.
\( \displaystyle \ce{C6H5OH + 3HNO3} \xrightarrow{\text{conc.}} \ce{C6H2(NO2)3OH + 3H2O} \)
D. Reaction of phenol with Zn dust — This matches I. Benzene. On heating, zinc dust takes the oxygen and phenol is reduced to benzene.
\( \ce{C6H5OH + Zn -> C6H6 + ZnO} \)
Shortcut: A-IV (Reimer-Tiemann gives the aldehyde) appears only in Option (2).
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| – | – | – | 10-06 S3 27-05 S1 | – |