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.

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:

Another example is:

2CH
3COOH ⇌ CH
3COO−
+ CH
3COOH+
2

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Wikipedia