Carbon hexoxide or carbon hexaoxide is an

oxide of carbon In chemistry, an oxocarbon or oxide of carbon is a chemical compound consisting only of carbon and oxygen. The simplest and most common oxocarbons are carbon monoxide (CO) and carbon dioxide (). Many other stable (practically if not thermodynamica ...

with an unusually large quantity of oxygen. The molecule has been produced and studied at cryogenic temperatures. The molecule is important in atmospheric chemistry and in the study of cold ices in the outer solar system and interstellar space. The substance could form and be present on Ganymede or

Triton Triton commonly refers to: * Triton (mythology), a Greek god * Triton (moon), a satellite of Neptune Triton may also refer to: Biology * Triton cockatoo, a parrot * Triton (gastropod), a group of sea snails * ''Triton'', a synonym of ''Triturus' ...

, moons in the outer solar system. The molecule consists of a six membered ring with five oxygen and one carbon atom, and one oxygen with a double bond with the carbon.

Shape

The molecule that has been observed has a C_s symmetry. The ring is not a flat hexagon but puckered with slightly different side lengths and angles (120°) from the regular hexagon. Going around the ring starting at the carbon to oxygen bond the interatomic distances are C–O: 1.362 Å O–O 1.491 Å, O–O 1.391 Å, O–O 1.391 Å, O–O 1.491 Å, and O–C 1.362 Å. The angles between the bonds are: O–C–O 120.4 °, C–O–O 115.7°, O–O–O 105.9°, and the opposite from carbon O–O–O 104.1°. For the double carbon to oxygen bond, the length is 1.185 Å and the angle from the single bonds is 119.6°.

Formation

In an experiment, carbon hexoxide was formed by irradiating solid carbon dioxide with electrons at an energy of 5000 eV at 10 K in a vacuum. The reaction proceeds by breaking

atomic oxygen There are several known allotropes of oxygen. The most familiar is molecular oxygen (O2), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (O3). Others are: *A ...

from carbon dioxide: : CO₂ → CO + O The atomic oxygen then reacts with carbon dioxide to form carbon trioxide, and similar reactions occur to generate the series of ring oxides

carbon tetroxide Carbon tetroxide or Oxygen carbonate ''(in its C2v isomer)'' is a highly unstable oxide of carbon with formula . It was proposed as an intermediate in the O-atom exchange between carbon dioxide () and oxygen () at high temperatures. The C2v iso ...

and carbon pentoxide, ultimately leading to the formation of carbon hexoxide in an

exothermic In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e ...

reaction. :CO₂ + O → O₂CO :O₂CO + O → O₃CO :O₃CO + O → O₄CO :O₄CO + O → O₅CO ΔH = −145.2 kJ mol⁻¹

Properties

Carbon hexoxide is stable up to 60 K. Vibrational

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

wavenumber In the physical sciences, the wavenumber (also wave number or repetency) is the ''spatial frequency'' of a wave, measured in cycles per unit distance (ordinary wavenumber) or radians per unit distance (angular wavenumber). It is analogous to temp ...

s include the most prominent ν₁ = 1876 cm⁻¹ for the most common isotopologue ¹²C¹⁶O₆.

Other isomers

Other possible isomers of carbon hexoxide are the C₂ form with a five and three membered ring, and the D_2d with two four membered rings. The D_2d O₃CO₃ isomer has a calculated C–O bond length of 1.391 Å, and an O–O length of 1.469 Å. The O–C–O bond angle is 94.1°. However these two isomers have not been observed. The equivalent carbon hexasulfide is also known from inert gas matrix study. It has C₂ symmetry with the same atomic arrangement as the hexoxide.

References

{{Inorganic compounds of carbon Oxocarbons