Explain why nucleophilic substitution reactions are not very common in phenols ?

Explanation

### Step-by-Step Solution:

1. **Understanding Phenols**:
- Phenols are compounds that contain a hydroxyl (-OH) group attached to an aromatic ring. The structure of phenol allows for resonance, which is the delocalization of electrons across the aromatic system.

2. **Resonance in Phenols**:
- In phenols, the oxygen atom in the hydroxyl group has two lone pairs of electrons. One of these lone pairs can participate in resonance with the π-electrons of the aromatic ring. This results in several resonance structures where the negative charge can be delocalized around the aromatic ring.

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