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Disproportionation or dismutation is used to describe two particular types of chemical reaction:[1]

  • A chemical reaction of the type: 2A → A' + A" where A, A' and A" are different chemical species. While the most common type is a redox reaction, other types are possible. For example: 2H2O → H3O+ + OH- is a disproportionation but is not a redox reaction.
  • A chemical reaction in which an element is simultaneously reduced and oxidized to form two different products.

The reverse of disproportionation is called comproportionation.


The first disproportionation reaction to be studied in detail was:

2 Sn2+ → Sn + Sn4+

This was examined using tartrates by Johan Gadolin in 1788. In the Swedish version of his paper he called it 'söndring'. (K. Sv. Vet. Acad. Handl. 1788, 186-197; Crells chem. Annalen 1790, I, 260-273).


3Cl2 + 6OH → 5Cl + ClO3 + 3H2O
As a reactant, the oxidation number of the elemental chlorine is 0. In the products, Cl has an oxidation number of −1, having been reduced; whereas the oxidation number of chlorine in the chlorate ion is +5, indicating that it has been oxidized.

2O2 + 2H+ → H2O2 + O2

2H2O2 → 2H2O + O2

2CO → C + CO2


  1. ^ International Union of Pure and Applied Chemistry. "disproportionation". Compendium of Chemical Terminology Internet edition.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Disproportionation". A list of authors is available in Wikipedia.
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