Benzene: All C-C bonds equal (1.39 Å), 6 delocalized pi electrons, planar; Huckel's Rule: (4n+2) pi $e^{-}$ + planar + cyclic + conjugated = aromatic; COT (8 pi $e^{-}$) is non-aromatic (non-planar), not anti-aromatic.

EAS Mechanism: $E^{+}$ generation → arenium ion (sigma complex, RDS, aromaticity lost) → $H^{+}$ loss (rearomatization); substitution not addition because of 36 kcal/mol resonance driving force.

5 EAS Reactions: Halogenation ($X^{+}$/Lewis acid), Nitration ($NO_{2}^{+}$/$H_{2}SO_{4}$), Sulfonation ($SO_{3}$, REVERSIBLE), FC Alkylation ($R^{+}$, rearranges + polyalkylates), FC Acylation (R$CO^{+}$, no rearrangement, no polyacylation).

Halogen Anomaly: -Cl, -Br etc. are o/p directors (via +M) but deactivating (via dominant -I) — the ONLY deactivating o/p directors; all other deactivators are meta.

Meta Directors: -$NO_{2}$, -CN, -CHO, -COOH, -COR — all withdraw by -M; FC reactions fail on these deactivated rings.