Aspirin is a commonly used non-steroidal anti-inflammatory drug which reduces fever, relieves mild pain and decreases swelling. It is prepared by numerous synthetic methods; of which the acetylation of Compound A with acetyl chloride is one of the easiest methods. However, Compound A itself needs to be prepared from Compound B under basic conditions by using carbon dioxide as a reagent. Interestingly, Compound B along with Compound C can be obtained by the air oxidation of Compound D. Compound C is a commonly used industrial solvent and gives a positive iodoform test and a negative Tollen’s test. Compound C easily forms 2,4-DNP derivative (Compound E). Compound C on reaction with Ba(OH)2 under heating conditions produces Compound F whose molecular formula is C6H10O.
The structures of Compound A and Compound B, respectively are
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → salicylic acid (Compound A) and phenol (Compound B)
The passage describes a chain of reactions leading to aspirin:
Aspirin is made by acetylating Compound A, so A is salicylic acid (2-hydroxybenzoic acid).
A is made from Compound B under basic conditions with carbon dioxide. This is the Kolbe reaction: sodium phenoxide reacts with \( \ce{CO2} \), and acidification gives salicylic acid. So B is phenol.
\( \displaystyle \ce{C6H5OH} \xrightarrow{\ce{NaOH}} \ce{C6H5ONa} \xrightarrow[\text{(ii) }\ce{H+}]{\text{(i) }\ce{CO2}} \ce{2-HOC6H4COOH} \)
The phenoxide ion is even more reactive than phenol towards electrophiles, so it reacts with the weak electrophile \( \ce{CO2} \), mainly at the ortho position. So A is salicylic acid and B is phenol.
Why the other options are incorrect
Option (2) phenol (A) and salicylic acid (B) — Incorrect. The two compounds are the right ones but in reverse order; phenol is the starting material and salicylic acid is the product acetylated to aspirin.
Option (3) phenol (A) and salicylaldehyde (B) — Incorrect. Salicylaldehyde is formed from phenol with \( \ce{CHCl3} \) and NaOH (Reimer–Tiemann reaction), not with \( \ce{CO2} \), and phenol is not acetylated to aspirin.
\( \displaystyle \ce{C6H5OH} \xrightarrow[\text{(ii) }\ce{H+}]{\text{(i) }\ce{CHCl3}\text{, aq. NaOH}} \ce{2-HOC6H4CHO} \)
Option (4) salicylaldehyde (A) and phenol (B) — Incorrect. Acetylating salicylaldehyde would give an aldehyde, not aspirin, and the \( \ce{CO2} \) reaction gives an acid, not an aldehyde.
NCERT (2026-27 edition):
Kolbe’s Reaction
