User:Jorge Stolfi/Oxocarbon test

An oxocarbon is a chemical compound consisting only of carbon and oxygen.

The simplest and most common oxocarbons are carbon monoxide (CO) and carbon dioxide (CO2). There are however many other stable or metastable oxides of carbon which rarely occur outside chemical plants and laboratories, such as carbon suboxide (O=C=C=C=O), and mellitic anhydride (C12O9).

Several new oxides, with various degrees of stability, have been synthesized since the 1990s. These include many oxides which are inherently unstable and can be observed only momentarily as intermediates in chemical reactions. Three important examples are the dicarbon monoxide radical (:C=C=O), carbon trioxide (CO3), and 1,2-dioxetanedione (C2O4). There are also many oxocarbons which are very reactive, and can be studied only in the gas phase, or under matrix isolation conditions.

Linear carbon dioxides
One family of carbon oxides has the general formula CnO2, or O=(C=)nO --- namely a linear chain of carbon atoms connected by double bonds, capped by oxygen atoms at both ends. The first members are
 * CO2 or O=C=O, the well-known carbon dioxide.
 * C2O2 or O=C=C=O, the extremely unstable ethylene dione.
 * C3O2 or O=C=C=C=O, the metastable carbon suboxide or tricarbon dioxide.
 * C4O2 or O=C=C=C=C=O, tetracarbon dioxide or 1,2,3-Butatriene-1,4-dione.
 * C5O2 or O=C=C=C=C=C=O, pentacarbon dioxide.

Some higher member of this family (for n = 17,19,21) have been detected in trace amounts in cryogenic matrix experiment

Radialene-type cyclic polyketones
Another family of oxocarbons that has attracted special attention are the cyclic radialene-type oxocarbons CnOn or (CO)n. They can be regarded as cyclic polymers of carbon monoxide, or n-fold ketones of n-carbon cycloalkanes. The first two members are carbon monoxide itself (CO) and the extremely unstable ethylene dione C2O2 or O=C=C=O. Theoretical studies suggest that the next four members — C3O3, C4O4, C5O5, and C6O6 — may be stable, but so far they have been synthesized only in trace amounts.

On the other hand, the anions of these oxocarbons are quite stable and have been known since the 19th century. They are, respectively, deltate (C3O32&minus;), squarate (C4O42&minus;), croconate (C5O52&minus;), and rhodizonate (C6O62&minus;). The aromaticity of these anions has been studied using theoretical methods.

New oxides
Many new stable or metastable oxides have been synthesized since the 1990s, such as:
 * C24O6 and C32O8, respectively cyclic trimer and tetramer of the biradical 3,4-dialkynyl-3-cyclobutene1,2-dione -C&equiv;C-(C4O2)-C&equiv;C- (1990)
 * C4O6, dioxane tetraketone or dimeric oxalic anhydride (1998)
 * C12O6 hexaoxotricyclobutabenzene (2006)

Polymeric carbon oxides
Carbon-oxygen polymers of relatively high molecular weight, with 3:2 atomic ratio can be obtained from carbon suboxide (spontaneously) or carbon monoxide (by compression to 5 GPA). Another carbon-oxygen polymer, with C:O ratio 5:1 or higher, is the classical graphite oxide (1859) and its single-sheet version graphene oxide.

Category:Oxocarbons Category:Carbon compounds Category:Oxygen compounds