Disproportionation

Synonyms

Dismutation

Definition

In chemistry, a disproportionation reaction is a type of chemical reaction in which two identical compounds react to form two or more new compounds of a dissimilar type. Usually, these involve reaction compounds containing an element in the same oxidation state reacting to form two compounds containing that element but with both higher and lower oxidation states, for example, in the Cannizzaro reaction with formaldehyde:

$$ 2\;\mathrm{H}\mathrm{CHO}\to \mathrm{HCOOH}+{\mathrm{CH}}_3\mathrm{O}\mathrm{H} $$

(1)

An example of a disproportionation reaction in which no redox chemistry takes place is the ionization of water:

$$ 2{\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}}_3{\mathrm{O}}^{+}+{\mathrm{O}\mathrm{H}}^{-} $$

(2)

See Also

• Fractionation

• Redox Potential