Comproportionation (alternatively referred to as con-, sym-, or synproportionation) is a special kind of chemical reaction. It is typically defined as when two chemical species containing the same element with different oxidation numbers react to yield a product species with the same intermediate oxidation state.
Comproportionation is special because it effectively turns different kinds of chemical inputs into multiples of a chemical output. In the figure below, two inputs (MHi and MLo) react to yield 2 outputs of MMed.
Image from Peng et al., 2023.
Encyclopedia Autocatalytica 