Formula CH2O2 | Molar mass 46.03 g/mol | |
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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 observed 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 as the key catalytic intermediate in the Shi epoxidation reaction. Other common derivatives employed in organic synthesis include dimethyldioxirane (DMDO) and the more reactive methyl(trifluoromethyl)dioxirane, which are prepared as dilute solutions (~0.1 M) by treatment of acetone and methyl trifluoromethyl ketone, respectively, with Oxone (2KHSO5·KHSO4·K2SO4). Difluorodioxirane, a gas (b.p ~ –80 - –90 °C), is one of the very few dioxirane derivatives that is stable in pure form at room temperature.
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.
