Electrophilic Substitution
A reaction in which an electrophile replaces a hydrogen atom on an aromatic ring.
Formula / equation
ArH + E⁺ → ArE + H⁺
Unit
Dimensionless
In depth
The ring attacks the electrophile to form a resonance-stabilised carbocation, which then loses a proton to restore aromaticity. Substituents already on the ring direct the incoming group: electron donors send it ortho and para, electron withdrawers send it meta.
Examples in the real world
Nitration of benzene with a nitric and sulfuric acid mixture; Friedel–Crafts alkylation and acylation.