Carbon pentaoxide, carbon pentoxide or tetraoxolan-5-one is an unstable molecular oxide of carbon. The molecule has been produced and studied at cryogenic temperatures. The molecule is important in

atmospheric chemistry Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earth's atmosphere and that of other planets is studied. It is a multidisciplinary approach of research and draws on environmental chemistry, physics, meteorol ...

and in the study of cold ices in the outer solar system and

interstellar space Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, predo ...

. 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 has a C₂ symmetry. It consists of a five membered ring with one carbon and four oxygen atoms. A fifth oxygen atom has a double bond to the carbon. Calculation has resulted in a theoretical structure. The pentagon is not regular, but varies in the length of its sides and angles. The distance between the oxygen atoms that are not attached to carbon is 1.406 Å, whereas the distance between one of these atoms and an oxygen attached to carbon is 1.457 Å. The carbon oxygen bond length is 1.376 Å. The double carbon to oxygen bond is the shortest at 1.180 Å. There is no carbon-to-carbon bond as there is only one carbon atom. The OOO bond angle is 100.2° and the OOC angle is 109.1°. The OCO bond angle is 125.4°.

Production

Carbon pentaoxide was produced by irradiating cryogenically frozen carbon dioxide with 5 keV electrons. The reaction mechanism is by carbon tetroxide reacting with an oxygen atom. This reaction releases 17.0 kJmol⁻¹. Formation from ozone and carbon dioxide is energetically unfavourable by 165.6 kJmol⁻¹, and

carbon trioxide Carbon trioxide (CO3) is an unstable oxide of carbon (an oxocarbon). The possible isomers of carbon trioxide include ones with molecular symmetry point groups ''Cs'', ''D3h'', and ''C2v.'' The ''C2v'' state, consisting of a dioxirane, has been ...

reacting with dioxygen molecules also would require 31.6 kJmol⁻¹.

Properties

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 te ...

s include the most prominent ν₁ 1912 cm⁻¹ for the most common

isotopologue In chemistry, isotopologues are molecules that differ only in their isotopic composition. They have the same chemical formula and bonding arrangement of atoms, but at least one atom has a different number of neutrons than the parent. An exampl ...

¹²C¹⁶O₅. Potential routes for decomposition are by forming carbon dioxide and ozone, or

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

and oxygen, or carbon trioxide and oxygen. Carbon pentaoxide is less volatile than carbon dioxide, remaining stable and solid until about 106K. An alternative theoretical structure, termed C_2v, has a spiro structure with one four-member ring and a three-member ring tied perpendicularly at the carbon atom. However, this is 166 kJmol⁻¹ higher in energy than the C₂ isomer, and thus less likely to be formed. This isomer has not been detected. The equivalent carbon pentasulfide is also known from inert gas matrix. It has C₂ symmetry with the same atomic topology as the pentoxide.

References

{{Inorganic compounds of carbon Oxocarbons