Peroxide

A peroxide contains an oxygen-oxygen unit, formally ${\mathrm{O}}_2^{2-}$ in an ionic description or an O-O single bond in compounds such as hydrogen peroxide. The oxygen oxidation state differs from that in an ordinary oxide.

Cleavage or transfer involving the oxygen-oxygen bond contributes to characteristic redox and radical chemistry. A peroxide is therefore not defined merely by having two oxygen atoms anywhere in its formula.

An organic peroxide that can initiate radical polymerization by O–O bond homolysis. Benzoyloxy radicals, and radicals formed by their further reaction, can initiate monomer addition.