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. For example, water undergoes autoprotolysis in the self-ionization of water reaction. It is a type of molecular autoionization.


 * 2 H2O <-> 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:


 * 2 NH3 <-> NH2- + NH4+

Another example is acetic acid:


 * 2 CH3COOH <-> CH3COO- + CH3COOH2+