The reactions in which a single reactant is oxidized and reduced is known as Disproporionation reactions.
The disproportionation reaction is given below
2H2O2 → 2H2O + O2
Above reaction is a disproportionation reaction because O is reduced in forming H₂O and oxidized in forming O₂
Disproportionation of H3PO3
When H3PO3 is heated, it gives two products. H3PO3 undergoes a disproportionation reaction when heated, yielding ortho phosphoric acid and phosphine.
4 H3PO3 → 3 H3PO4 + PH3