Carbon trioxide

For polyatomic ion CO²⁻
₃, see Carbonate. For the UK postal district, see CO postcode area.

Carbon trioxide (CO₃) is an unstable oxide of carbon (an oxocarbon). The possible isomers of carbon trioxide include ones with molecular symmetry point groups C_s, D_3h, and C_2v. The C_2v state, consisting of a dioxirane, has been shown to be the ground state of the molecule.^[1] Carbon trioxide should not be confused with the stable carbonate ion (CO²⁻
₃).

Carbon trioxide

The Cs, D3h, and C2v isomers of carbon trioxide
Names
IUPAC names Carbon trioxide C2v isomer: Dioxiran-3-one D3h isomer: Carbonate radical
Systematic IUPAC name C2v isomer: Peroxycarbonic anhydride D3h isomer: Trioxidocarbon(2•)
Other names Cs isomer: Oxidooxymethanone Peroxycarbonite radical
Identifiers
CAS Number	12144-05-7
3D model (JSmol)	Cs: Interactive image D3h: Interactive image C2v: Interactive image
PubChem CID	19817254
InChI InChI=1S/CO3/c2-1-3-4-1 Key: NPDDCAZCWJWIBW-UHFFFAOYSA-N
SMILES Cs: O=[C]O[O] D3h: O=C([O])[O] C2v: O=C1OO1
Properties
Chemical formula	CO3
Molar mass	60.008 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Carbon trioxide can be produced, for example, in the drift zone of a negative corona discharge by reactions between carbon dioxide (CO₂) and the atomic oxygen (O) created from molecular oxygen by free electrons in the plasma.^[2] Another reported method is photolysis of ozone O₃ dissolved in liquid CO₂, or in CO₂/SF₆ mixtures at −45 °C, irradiated with light of 253.7 nm. The formation of CO₃ is inferred but it appears to decay spontaneously by the route

2 CO₃ → 2 CO₂ + O₂

with a lifetime much shorter than 1 minute.^[3] Carbon trioxide can be made by blowing ozone at dry ice (solid CO₂), and it has also been detected in reactions between carbon monoxide (CO) and molecular oxygen (O₂). Along with the ground state C_2v isomer,^[4] the first spectroscopic detection of the D_3h isomer was in electron-irradiated ices of carbon dioxide.^[5]