Dioxirane

In chemistry, dioxirane (systematically named dioxacyclopropane, also known as methylene peroxide or peroxymethane) is an organic compound with formula. The molecule consists of a ring with one methylene and two oxygen atoms. It is of interest as the smallest cyclic organic peroxide, but otherwise it is of little practical value.

Synthesis
Dioxirane is highly unstable and the majority of studies of it have been computational; it has been detected during the low temperature (–196 °C) reaction of ethylene and ozone, although even at these temperatures such a mixture can be explosive. Its formation is thought to be radical in nature, preceding via a Criegee intermediate. Microwave analysis has indicated C-H, C-O and O-O bond lengths of 1.090, 1.388 and 1.516 Å respectively. The very long and weak O-O bond (c.f. hydrogen peroxide O-O = 1.47 Å) is the origin of its instability.

Other dioxiranes
Dioxiranes are derivatives of this parent in which the hydrogens are replaced by other groups. Difluorodioxirane, which boils at about –80 to –90 °C, is one of the very few dioxirane derivatives that is stable in pure form at room temperature and is thermodynamically stable (ΔH° = –104 kcal/mol). Dimesityldioxirane is another relatively stable derivative which has been characterized by X-ray crystallography.

Dimethyldioxirane (DMDO) and the still more reactive methyl(trifluoromethyl)dioxirane have seen some use in organic synthesis, Dioxiranes are intermediate in the Shi epoxidation reaction.