Why does benzene undergo electrophilic substitution reactions easily and nucleophilic substitutions with difficulty?

Explanation

**Step-by-Step Solution:**

1. **Understanding Benzene Structure:**
- Benzene (C6H6) is a planar, cyclic molecule with a ring structure. Each carbon atom in benzene is sp² hybridized, leading to a planar arrangement.

2. **Delocalized Electrons:**
- The benzene ring contains delocalized π electrons, which are spread over the entire ring structure. This delocalization creates a region of high electron density above and below the plane of the ring.

3. **Electrophilic Substitution Reactions:**
- Electrophiles are species that are electron-deficient and seek out electrons. Since benzene is electron-rich due to its delocalized electrons, it readily attracts electrophiles.
- The presence of electron-rich π electrons makes benzene highly reactive towards electrophiles, facilitating electrophilic substitution reactions. This is why benzene undergoes electrophilic substitution reactions easily.

4. **Nucleophilic Substitution Reactions:**
- Nucleophiles are species that are electron-rich and have a tendency to donate electrons. Since benzene itself is electron-rich, it repels other electron-rich species (nucleophiles).
- This repulsion makes it difficult for nucleophiles to attack the benzene ring, resulting in nucleophilic substitution reactions being less favorable or difficult to carry out.

5. **Conclusion:**
- In summary, benzene undergoes electrophilic substitution reactions easily due to its electron-rich nature, which attracts electron-deficient electrophiles. Conversely, nucleophilic substitution reactions are difficult because the electron-rich nucleophiles are repelled by the electron-rich benzene.

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