Lyonium ion

In chemistry, a lyonium ion is the cation derived by the protonation of a solvent molecule.^[1] For example, a hydronium ion is formed by the protonation of water, and CH₃OH+2 is the cation formed by the protonation of methanol.

Its counterpart is a lyate ion, the anion formed by the deprotonation of a solvent molecule.

Lyonium and lyate ions, resulting from molecular autoionization, contribute to the molar conductivity of protolytic solvents.

Examples

Lyate ion		Original solvent		Lyonium ion
name	formula	name	formula	name	formula
Fluoride	F−	Hydrogen fluoride	HF	Fluoronium	H2F+
Hydroxide	OH−	Water	H2O	Hydronium	H3O+
Azanide	NH−2	Ammonia	NH3	Ammonium	NH+4
Methanide	CH−3	Methane	CH4	Methanium	CH+5
Methoxide	CH3O−	Methanol	CH3OH	Methyloxonium	CH3OH+2

See also

• Lyate ion, a deprotonated solvent molecule
• Onium ion, a protonated molecule more generally
• Ion transport number
• Ionic atmosphere