Synproportionation

Synproportionation or comproportionation is a concept in chemistry and is a redox reaction where two reactants that share an atom but differ in oxidation number react to a single reaction product.

Examples:
* Potassium permanganate contains manganese with oxidation number of +7 and reacts with a manganese compound having oxidation number +2 to yield Manganese(IV) oxide (manganese dioxide) with oxidation number +4, potassium hydroxide and water.
* In chalcogen chemistry 15Se + SeCl₄ + 4AlCl₃ -> Na [AlCl] ₄ + 3Se₈ [AlCl₄] ₂. [http://www.chem.fsu.edu/editors/alabugin/chemical_reviews_galley.pdf]
* In volcanic eruptions, the redox reaction 2H₂S(g) + SO₂(g) -> 3S(s) + 2H₂O(g).

It is the chemical opposite to disproportionation, where two or more atoms originally having the same oxidation state react with other chemical(s) to give ions with different oxidation numbers.

References

* Translated from German Wiki original