Cations derived formally by the addition of a hydron or other cationic species to any position of an arene, e.g. C6H7+, benzenium. The term includes:
- Arenium σ-adducts (Wheland intermediates) (which are considered to be intermediates in electrophilic aromatic substitution reactions) and other cyclohexadienyl cations.
- Arenium π-adducts, such as:
[σ-adduct (sigma-adduct), π-adduct (pi-adduct)].