dioxirane
{{Distinguish|Dioxane}}
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 424858886
| ImageFileL1 = Dioxirane.svg
| ImageSizeL1 = 80px
| ImageFileR1 = Dioxirane-stick.png
| ImageFile2 = Dioxirane3D.png
| ImageSize2 = 120px
| PIN= Dioxirane
| SystematicName= Dioxacyclopropane
| OtherNames = 1,2-Dioxacyclopropane
Methylene peroxide
Peroxymethane
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 157-26-6
| PubChem = 449520
| SMILES = C1OO1
| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
| ChemSpiderID = 396025
| InChI = 1/CH2O2/c1-2-3-1/h1H2
| InChIKey = ASQQEOXYFGEFKQ-UHFFFAOYAK
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChI = 1S/CH2O2/c1-2-3-1/h1H2
| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}
| StdInChIKey = ASQQEOXYFGEFKQ-UHFFFAOYSA-N
}}
|Section2={{Chembox Properties
| Formula = CH2O2
| MolarMass = 46.03 g/mol
| Appearance =
| Density =
| MeltingPt =
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| Solubility =
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|Section3={{Chembox Hazards
| MainHazards =
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In chemistry, dioxirane (systematically named dioxacyclopropane, also known as methylene peroxide or peroxymethane) is an organic compound with formula {{chem|CH|2|O|2}}. 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
{{See also|Epoxidation with dioxiranes}}
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,{{cite journal|last1=Lovas|first1=F.J.|last2=Suenram|first2=R.D.|title=Identification of dioxirane (H2) in ozone-olefin reactions via microwave spectroscopy|journal=Chemical Physics Letters|date=November 1977|volume=51|issue=3|pages=453–456|doi=10.1016/0009-2614(77)85398-0|bibcode=1977CPL....51..453L}} although even at these temperatures such a mixture can be explosive.{{cite journal|last1=Suenram|first1=R. D.|last2=Lovas|first2=F. J.|title=Dioxirane. Its synthesis, microwave spectrum, structure, and dipole moment|journal=Journal of the American Chemical Society|date=August 1978|volume=100|issue=16|pages=5117–5122|doi=10.1021/ja00484a034}} 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 (cf. hydrogen peroxide 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 (DMD or DMDO) and trifluoromethyl-methyldioxirane (TFD). DMDO and the still more reactive methyl(trifluoromethyl)dioxirane have seen some use in organic synthesis,{{cite journal|journal=Pure Appl. Chem.| volume=67 |issue=5 |pages=811–822 |year=1995 |title=Dioxirane oxidations: Taming the reactivity-selectivity principle|author1=Ruggero Curci |author2=Anna Dinoi |author3=Maria F. Rubino | url=http://www.iupac.org/publications/pac/1995/pdf/6705x0811.pdf |doi=10.1351/pac199567050811| s2cid=44241053 }} 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.Adam, W.; Curci, R.; Edwards, J. O. Acc. Chem. Res. 1989, 22, 205. (1)center
Dioxiranes are intermediate in the Shi epoxidation reaction.
The latter is effective for chemoselective oxidations of C-H and Si-H bonds.Asensio, G.; González-Núñez, M. E.; Biox Bernardini, C.; Mello, R.; Adam, W. J. Am. Chem. Soc. 1993, 115, 7250. 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, 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).{{Cite journal |last=Kraka |first=Elfi |last2=Konkoli |first2=Zoran |last3=Cremer |first3=Dieter |last4=Fowler |first4=Joseph |last5=Schaefer |first5=Henry F. |date=1996-01-01 |title=Difluorodioxirane: An Unusual Cyclic Peroxide |url=https://pubs.acs.org/doi/10.1021/ja961983w |journal=Journal of the American Chemical Society |language=en |volume=118 |issue=43 |pages=10595–10608 |doi=10.1021/ja961983w |issn=0002-7863|url-access=subscription }}{{Cite journal |last=Russo |first=Antonio |last2=DesMarteau |first2=Darryl D. |date=1993 |title=Difluorodioxirane |url=https://onlinelibrary.wiley.com/doi/10.1002/anie.199309051 |journal=Angewandte Chemie International Edition in English |language=en |volume=32 |issue=6 |pages=905–907 |doi=10.1002/anie.199309051 |issn=0570-0833|url-access=subscription }} Dimesityldioxirane is another relatively stable derivative which has been characterized by X-ray crystallography.{{Cite journal |last=Sander |first=Wolfram |last2=Schroeder |first2=Kerstin |last3=Muthusamy |first3=Sengodagounder |last4=Kirschfeld |first4=Andreas |last5=Kappert |first5=Wilhelm |last6=Boese |first6=Roland |last7=Kraka |first7=Elfi |last8=Sosa |first8=Carlos |last9=Cremer |first9=Dieter |date=1997-08-01 |title=Dimesityldioxirane |url=https://pubs.acs.org/doi/10.1021/ja964280n |journal=Journal of the American Chemical Society |language=en |volume=119 |issue=31 |pages=7265–7270 |doi=10.1021/ja964280n |issn=0002-7863|url-access=subscription }}