Autoprotolysis

In chemistry, autoprotolysis is a chemical reaction in which 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.[1] For example, water undergoes autoprotolysis in the self-ionization of water reaction. It is a type of molecular autoionization.

${\displaystyle {\ce {2H2O <=> OH- + H3O+}}}$

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:

${\displaystyle {\ce {2NH3 <=> NH2- + NH4+}}}$

Another example is acetic acid:

${\displaystyle {\ce {2CH3COOH <=> CH3COO- + CH3COOH2+}}}$