Product 'A' is:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Salicylic acid
This is Kolbe’s reaction. Phenol is first converted by NaOH into sodium phenoxide. The phenoxide ion is even more strongly activated than phenol, so it undergoes electrophilic substitution with carbon dioxide, a weak electrophile, mainly at the ortho position. Acidifying the sodium salicylate with HCl gives salicylic acid (2-hydroxybenzoic acid).
\( \ce{C6H5OH + NaOH -> C6H5ONa + H2O} \)
\( \ce{C6H5ONa + CO2} \xrightarrow[\text{4-7 atm}]{\text{400 K}} \text{ o-}\ce{HOC6H4COONa} \)
\( \text{o-}\ce{HOC6H4COONa + HCl ->} \text{ o-}\ce{HOC6H4COOH + NaCl} \)
Why the other options are incorrect
Option (1) Salicylaldehyde — Incorrect. It is the product of the Reimer–Tiemann reaction, phenol with \( \ce{CHCl3} \) and aqueous NaOH followed by acid; \( \ce{CO2} \) introduces –COOH, not –CHO.
Option (2) Benzoic acid — Incorrect. The –OH group of phenol is not removed in this reaction; the product keeps it next to the new –COOH group.
Option (3) p-Chlorobenzoic acid — Incorrect. HCl only acidifies the salt; no chlorine is put on the ring, and the –OH group stays.
NCERT (2026-27 edition):
Kolbe’s Reaction
