Question

An organic compound 'A' having molecular formula C₆H₆O gives a characeristic colour with aqueous FeCl₃ solution. When 'A' is treated with CO₂ and NaOH at 400K under pressure, compound 'B' is obtained. The compound 'B' upon acidification gives compound 'C' which reacts with acetyl chloride to form 'D'. It is a polular pain killer. Deduce the structures of A, B, C and D.

Answer 1

The Structural Formulas:

Compound A (phenol): C₆H₅OH

Compound B (salicylic acid): C₆H₄(OH)(COOH)

Compound C (benzoic acid): C₆H₅COOH

Compound D (aspirin): C₈H₈O₄ (acetyl salicylic acid) .

Compound A:

The molecular formula of compound A is C₆H₆O. This formula suggests that A is an aromatic compound with a hydroxyl group (-OH) attached to it.

The violet color with neutral FeCl₃ is a characteristic reaction of phenols, which are a type of aromatic compound with a hydroxyl group.

Therefore, compound A is most likely phenol.

Compound B:

When phenol (compound A) is treated with CO₂ and NaOH at 400 K under pressure, it undergoes the Kolbe-Schmitt reaction to form salicylic acid. Salicylic acid is a benzoic acid derivative with a hydroxyl group in the ortho position.

The molecular formula of salicylic acid is C₇H₆O₃.

Compound C:

Salicylic acid (compound B) can be acidified to form its corresponding carboxylic acid, which is benzoic acid.

Benzoic acid has the molecular formula C₇H₆O₂.

Compound D:

Benzoic acid (compound C) can react with acetyl chloride to form aspirin, which is a popular pain killer.

Aspirin is an acetyl derivative of salicylic acid. The molecular formula of aspirin is C₉H₈O₄.