In
chemistry, autoprotolysis is a
chemical reaction
A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breakin ...
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
In chemistry, molecular autoionization (or self-ionization) is a chemical reaction between molecules of the same substance to produce ions. If a pure liquid partially dissociates into ions, it is said to be self-ionizing. In most cases the oxida ...
.
:
2H2O <=> OH- + H3O+
Any solvent that contains both acidic hydrogen and lone pairs of electrons to accept can undergo autoprotolysis.
For example,
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
in its purest form may undergo autoprotolysis:
:
2NH3 <=> NH2- + NH4+
Another example is
acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
:
:
2CH3COOH <=> CH3COO- + CH3COOH2+
References
Acid–base chemistry
Equilibrium chemistry
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