Autoprotolysis

In autoprotolysis a proton is transferred between two identical molecules, one of which acts as a Brønsted acid, releasing a proton which is accepted by the other molecule acting as a Brønsted base. For example, water undergoes autoprotolysis in the self-ionization of water reaction.

2H
2O ⇌ OH−
+ H
3O+

Any solvent that contains both acidic hydrogen and lone pairs of electrons to accept H⁺ can undergo autoprotolysis.

For example, ammonia in its purest form may undergo autoprotolysis:

2NH
3 ⇌ NH−
2 + NH+
4

References

Autoprotolysis. IUPAC gold book. doi:10.1351/goldbook.A00531.