Editing Ammonium (section)

== Organic ions ==
{{See also|Amine}}
The hydrogen atoms in the ammonium ion can be substituted with an [[alkyl]] group or some other organic group to form a '''substituted ammonium ion''' ([[IUPAC]] nomenclature: '''aminium ion'''). Depending on the number of organic groups, the ammonium cation is called a [[Primary (chemistry)|primary]], [[Secondary (chemistry)|secondary]], [[Tertiary (chemistry)|tertiary]], or [[Quaternary (chemistry)|quaternary]]. Except the quaternary ammonium cations, the organic ammonium cations are weak acids.

An example of a reaction forming an ammonium ion is that between [[dimethylamine]], {{chem2|(CH3)2NH}}, and an acid to give the [[dimethylammonium]] cation, {{chem2|[(CH3)2NH2]+}}:
: [[File:Dimethylammonium-formation-2D.png|class=skin-invert-image|400px]]

Quaternary ammonium cations have four organic groups attached to the nitrogen atom, they lack a hydrogen atom bonded to the nitrogen atom. These cations, such as the [[tetra-n-butylammonium|tetra-''n''-butylammonium]] cation, are sometimes used to replace sodium or potassium ions to increase the [[solubility]] of the associated anion in organic [[solvents]]. Primary, secondary, and tertiary ammonium salts serve the same function but are less [[lipophilic]]. They are also used as [[phase-transfer catalysts]] and [[surfactant]]s.

An unusual class of organic ammonium salts is derivatives of amine [[radical (chemistry)|radical]] cations, {{chem2|[•NR3]+}} such as [[tris(4-bromophenyl)ammoniumyl hexachloroantimonate]].