Disproportionation Definition in Chemistry

It's a chemical reaction that produces two or more dissimilar products

In disproportionation, a chemical species is simultaneously oxidized and reduced to form two dissimilar products.
In disproportionation, a chemical species is simultaneously oxidized and reduced to form two dissimilar products. PM Images, Getty Images
by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
Updated November 30, 2018

Disproportionation is a chemical reaction, typically a redox reaction, where a molecule is transformed into two or more dissimilar products. In a redox reaction, the species is simultaneously oxidized and reduced to form at least two different products.


Disproportionation reactions follow the form:

2A → A' + A"

where A, A', and A" are all different chemical species.

The reverse reaction of disproportionation is called comproportionation.

Examples: Hydrogen peroxide converting into water and oxygen is a disproportionation reaction.

2 H2O2 → H2O + O2

Water dissociating into H3O+ and OH- is an example of a disproportionation reaction that is not a redox reaction.