In chemistry dioxirane is a heterocyclic compound composed of one carbon and two oxygen atoms; it may be thought of as the smallest cyclic organic peroxide. The compound is highly unstable and has never been isolated at room temperature. Compounds containing dioxirane as a functional group, called dioxiranes, often possess better stability and are used in organic synthesis as oxidizing reagents, most notably in the Shi epoxidation reaction. A relatively stable dioxirane in common use is dimethyldioxirane (DMDO) which is derived from acetone.