Why does the arenium ion intermediate (Wheland intermediate) possess a substantial positive charge d — Aromatic Hydrocarbons Chemistry Question
Question
Why does the arenium ion intermediate (Wheland intermediate) possess a substantial positive charge distribution over the remaining five $sp^2$ hybridized carbon atoms, rather than localizing the positive charge entirely on the carbon adjacent to the site of attack?
💡 Solution & Explanation
Once the electrophile attacks, one carbon becomes $sp^3$ hybridized. The remaining five $p$ -orbitals remain conjugated. The 4 remaining $\pi$ electrons are delocalized across these five $p$ -orbitals, effectively spreading the positive charge over the ortho and para positions relative to the $sp^3$ carbon, generating 3 primary resonance structures.