What is "carbon suboxide"

n. (context inorganic compound English) The gas C₃O₂, having a heterocumulene structure O=C=C=C=O

Carbon suboxide, or tricarbon dioxide, is an oxide of carbon with chemical formula CO or O=C=C=C=O. Its four cumulative double bonds make it a cumulene. It is one of the stable members of the series of linear oxocarbons O=C=O, which also includes carbon dioxide (CO) and pentacarbon dioxide (CO).

The substance was discovered in 1873 by Benjamin Brodie by subjecting carbon monoxide to an electric current. He claimed that the product was part of a series of "oxycarbons" with formulas CO, namely C, CO, CO, CO, CO, ..., and to have identified the last two; however only CO is known. In 1891 Marcellin Berthelot observed that heating pure carbon monoxide at about 550 °C created small amounts of carbon dioxide but no trace of carbon, and assumed that a carbon-rich oxide was created instead, which he named "sub-oxide". He assumed it was the same product obtained by electric discharge and proposed the formula CO. Otto Diels later stated that the more organic names dicarbonyl methane and dioxallene were also correct.

It is commonly described as an oily liquid or gas at room temperature with an extremely noxious odor.