Summary
Electrophilic aromatic substitution reactions are the cornerstone of aromatic chemistry, proceeding via generation of reactive electrophilic species and formation of a resonance-stabilized carbocation intermediate. The reactivity and orientation of aromatic substitution are heavily influenced by substituent effects—both inductive and resonance—which dictate whether groups are activating or deactivating and whether they direct substitution to ortho, meta, or para positions. Friedel–Crafts alkylation/acylation reactions utilize these principles but require careful control to avoid rearrangements and polyalkylation. Additionally, aromatic compounds can undergo nucleophilic substitution via a stabilized Meisenheimer complex or via a benzyne intermediate under harsh conditions, providing versatility in synthetic routes.