Benzene undergoes electrophilic substitution rather than addition because substitution
- A. preserves the stable delocalised pi system
- B. produces a smaller molecule
- C. requires no catalyst
- D. is always exothermic
Explanation
Addition would destroy the aromatic sextet and lose the large resonance stabilisation, whereas replacing a hydrogen leaves the delocalised ring intact. This is why benzene reacts with bromine only in the presence of a halogen carrier and gives bromobenzene rather than a dibromo addition product. Nitration, sulphonation and Friedel Crafts reactions follow the same pattern.