In chemistry, dioxirane (systematically named dioxacyclopropane, also known as methylene peroxide or peroxymethane) is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with formula . The molecule consists of a ring with one methylene and two

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

atoms. It is of interest as the smallest cyclic organic

peroxide In chemistry, peroxides are a group of Chemical compound, compounds with the structure , where the R's represent a radical (a portion of a complete molecule; not necessarily a free radical) and O's are single oxygen atoms. Oxygen atoms are joined ...

, but otherwise it is of little practical value.

Synthesis

Dioxirane is highly unstable and the majority of studies of it have been

computational A computation is any type of arithmetic or non-arithmetic calculation that is well-defined. Common examples of computation are mathematical equation solving and the execution of computer algorithms. Mechanical or electronic devices (or, historic ...

; it has been detected during the low temperature (–196 °C) reaction of

ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...

and

ozone Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ...

, 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 A Criegee intermediate (also called a Criegee zwitterion or Criegee biradical) is a carbonyl oxide with two charge centers. These chemicals may react with sulfur dioxide and nitrogen oxides in the Earth's atmosphere, and are implicated in the f ...

. Microwave analysis has indicated C-H, C-O and O-O

bond length In molecular geometry, bond length or bond distance is defined as the average distance between Atomic nucleus, nuclei of two chemical bond, bonded atoms in a molecule. It is a Transferability (chemistry), transferable property of a bond between at ...

s of 1.090, 1.388 and 1.516 Å respectively. The very long and weak O-O bond (cf.

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...

O-O = 1.47 Å) is the origin of its instability.

Other dioxiranes

Beyond the parent dioxirane, which is mainly of theoretical interest, more common dioxiranes are

dimethyldioxirane Dimethyldioxirane (DMDO) is the organic compound with the formula . It is the dioxirane derived from acetone and can be viewed as the monomer of acetone peroxide. It is a powerful selective oxidizing agent that finds some use in organic synthesis ...

(DMD or DMDO) and trifluoromethyl-methyldioxirane (TFD). DMDO and the still more reactive methyl(trifluoromethyl)dioxirane have seen some use in

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

, These dioxiranes may be produced through the action of KHSO₅ on carbonyl compounds. Because of their low-lying σ*_O-O orbital, they are highly electrophilic oxidants and react with unsaturated functional groups, Y-H bonds (yielding oxygen insertion products), and heteroatoms. ''(1)'' DioxGen

Dioxiranes are intermediate in the

Shi epoxidation The Shi epoxidation is a chemical reaction described as the asymmetric epoxidation of alkenes with oxone (potassium peroxymonosulfate) and a fructose-derived catalyst (1). This reaction is thought to proceed via a dioxirane intermediate, generate ...

reaction. The latter is effective for chemoselective oxidations of C-H and Si-H bonds. Although this class of reagents is most famous for the epoxidation of alkenes, dioxiranes have been used extensively for other kinds of oxidations as well.

Difluorodioxirane Difluorodioxirane (CF2O2) is a rare, stable member of the dioxirane family, known for a single oxygen-oxygen bond (O-O). Unlike most dioxiranes that decompose quickly, difluorodioxirane is surprisingly stable at room temperature, making it poten ...

, 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 (Δ''H''° = –104 kcal/mol).

Dimesityldioxirane Dimesityldioxirane is a substituted dioxirane with two mesityl groups attached to the dioxirane carbon. It is a colorless crystalline substance stable in its solid state around -20 °C. Structure The molecule possesses approximately C2 sy ...

is another relatively stable derivative which has been characterized by X-ray crystallography.

References

{{Functional group Dioxiranes Functional groups

Synthesis

Other dioxiranes

See also

References