How is aspirin prepared ?

Explanation

**Step-by-Step Solution for the Preparation of Aspirin:**

1. **Identify the Starting Material**: The preparation of aspirin begins with salicylic acid, which has the chemical formula C7H6O3.

2. **Reagents Required**: The main reagents needed for the synthesis of aspirin are acetic anhydride (C4H6O3) or acetyl chloride (C2H3ClO) and a catalyst, typically an acid such as sulfuric acid (H2SO4) or phosphoric acid (H3PO4).

3. **Reaction Mechanism**:
- When salicylic acid reacts with acetic anhydride (or acetyl chloride), the hydroxyl group (-OH) of salicylic acid is replaced by an acetyl group (-O-C(=O)-CH3).
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