Aqueous Solutions Aqueous solutions are those solutions where water is the solvent. The arenes are a homologous series of aromatic hydrocarbons, which have a ring structure of six carbon atoms, with alternating single and double bonds. This closed ring structure has a very high stability and these aromatic compounds undergo substitution reactions in order to preserve the configuration of the ring structure. Although aromatic compounds are unsaturated, they do not readily undergo addition reactions, instead undergoing electrophilic substitution to preserve the stability of the aromatic ring. Aromatic compounds readily undergo substitution reactions that preserve the aromatic structure of the ring.
Aromatic stability is explained by resonance.
The Arrhenius concept of bases regard substance which provides hydroxyl ions as a result of dissociation and ionisation in aqueous solution as being bases. The Arrhenius concept of neutralisation involves the reaction in which a hydrogen ion and a hydroxide ion combine to form water. The Arrhenius concept of acids, gave the first understanding of the true nature of acids in aqueous solution. Arrhenius proposed that acids are substances which give rise to the hydrogen ions in solution and that bases are substances that give rise to hydroxyl ions in solution. It is the ionisation of the acid which gives rise to these hydrogen ions and thus also gives rise to the acidic properties.