Despite possessing a high degree of unsaturation (Degree of Unsaturation = 4), benzene is remarkably — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Benzene's $6 \pi$ electrons are completely delocalized in a closed continuous loop, conferring exceptional thermodynamic stability known as resonance energy ($\approx 151 \text{ kJ/mol}$). An addition reaction would convert two $sp^2$ carbons to $sp^3$, breaking the continuous conjugation and severely decreasing the molecule's stability. Thus, substitution (which retains the aromatic ring) is preferred.