An organic compound 'A' having molecular formula `C_(6)H_(6)O` gives a characeristic colour with aqueous `FeCl_(3)` solution. When 'A' is treated with `CO_(2)` and `NaOH` at `400 K` 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.

Explanation

To solve the problem step by step, we will identify the compounds A, B, C, and D based on the given information.

### Step 1: Identify Compound A
- The molecular formula of compound A is \( C_6H_6O \).
- Given that it gives a characteristic color with aqueous \( FeCl_3 \) solution, we can conclude that compound A is **phenol**.
- **Structure of A**:
- Phenol has the structure:
\[
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