15.2 A general mechanism for electrophilic aromatic substitution(芳香族亲电取代反 应机理): Arenium ions(芳基离 子) a considerable body of experimental evidence indicates that electrophiles attack the Isystem of benzene to form a delocalized nonaromatic carbocation known as an arenium ion or sometimes as a complex)15.2 A general mechanism for electrophilic aromatic substitution（芳香族亲电取代反 应机理）: Arenium ions（芳基离 子） A considerable body of experimental evidence indicates that electrophiles attack the πsystem of benzene to form a delocalized nonaromatic carbocation known as an arenium ion (or sometimes as a σcomplex) π