The reaction of `p-`aminophenol with one mole of acetyl chloride in presence of pyridine gives :

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Answer

To solve the problem regarding the reaction of p-aminophenol with one mole of acetyl chloride in the presence of pyridine, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactants are p-aminophenol (C6H4(OH)(NH2)) and acetyl chloride (CH3C(=O)Cl).
- p-Aminophenol has an amino group (-NH2) at the para position to the hydroxyl group (-OH) on the benzene ring.

2. **Understand the Role of Pyridine**:
- Pyridine acts as a basic solvent and helps in the reaction by deprotonating the amino group, making it a better nucleophile.

3. **Nucleophilic Attack**:
- The nitrogen atom in the amino group (-NH2) is more nucleophilic than the oxygen in the hydroxyl group (-OH) due to its lower electronegativity.
- The nitrogen will attack the carbonyl carbon of acetyl chloride, leading to the formation of an acylated product.

4. **Formation of the Intermediate**:
- The nucleophilic attack results in the formation of an intermediate where the nitrogen is bonded to the carbonyl carbon, and a chlorine atom is released as a leaving group.
- This intermediate can be represented as:
\[ C6H4(OH)(NH)(C(=O)CH3)^{+} \]
- Here, the nitrogen has a positive charge because it is forming four bonds (two from hydrogen and one from the carbonyl carbon).

5. **Elimination of Chloride Ion**:
- The positively charged nitrogen can stabilize itself by eliminating a proton (H+) to restore its neutral state.
- The chlorine ion (Cl-) is released during this process.

6. **Final Product Formation**:
- The final product is an N-acetyl derivative of p-aminophenol, which can be represented as:
\[ C6H4(OH)(NHCOCH3) \]
- This structure consists of the unchanged hydroxyl group, the amino group now acylated to form an amide, and the acetyl group (COCH3) attached to the nitrogen.

7. **Conclusion**:
- The product formed from the reaction of p-aminophenol with acetyl chloride in the presence of pyridine is N-acetyl-p-aminophenol.