Disproportionation Definition in Chemistry

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

Scientist holding a flask with evaporating liquid

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By
Anne Marie Helmenstine, Ph.D.
Chemistry Expert
  • Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
  • B.A., Physics and Mathematics, Hastings College
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.
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Anne Marie Helmenstine, Ph.D.
Updated October 03, 2019

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.

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Helmenstine, Anne Marie, Ph.D. "Disproportionation Definition in Chemistry." ThoughtCo, Aug. 28, 2020, thoughtco.com/definition-of-disproportionation-605037. Helmenstine, Anne Marie, Ph.D. (2020, August 28). Disproportionation Definition in Chemistry. Retrieved from https://www.thoughtco.com/definition-of-disproportionation-605037 Helmenstine, Anne Marie, Ph.D. "Disproportionation Definition in Chemistry." ThoughtCo. https://www.thoughtco.com/definition-of-disproportionation-605037 (accessed September 25, 2021).