What is a coupling reaction?

Explanation

### Step-by-Step Solution:

1. **Definition of Coupling Reaction**:
A coupling reaction is a type of chemical reaction where two molecules combine to form a larger molecule, typically involving an electrophilic substitution mechanism.

2. **Involvement of Diazonium Salts**:
In coupling reactions, diazonium salts react with aromatic compounds that have electron-rich groups. These electron-rich groups can include functional groups such as -OH (hydroxyl) and -NH2 (amino).

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