Oxocarbon

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 thermodynamically) or metastable oxides of carbon are known, but they are rarely encountered, such as carbon suboxide ( or ) and mellitic anhydride (). Many other oxides are known today, most of them synthesized since the 1960s. Some of these new oxides are stable at room temperature. Some are metastable or stable only at very low temperatures, but decompose to simpler oxocarbons when warmed. Many are inherently unstable and can be observed only momentarily as intermediates in chemical reactions or are so reactive that they exist only in gas phase or have only been detected by matrix isolation. Graphene oxide and other stable polymeric carbon oxides with unbounded molecular structures exist. Carbon dioxide (CO2) occurs widely in nature, and was incidentally produced by humans since pre-historical times, by breathing, the combustion of carbon-containing substances and fermentation of foods such as beer and bread. It was gradually recognized as a chemical substance, formerly called spiritus sylvestris ("forest spirit") or "fixed air", by various chemists in the 17th and 18th centuries. Carbon monoxide may occur in combustion, too, and was used (though not recognized) since antiquity for the smelting of iron from its ores. Like the dioxide, it was described and studied in the West by various alchemists and chemists since the Middle Ages. Its true composition was discovered by William Cruikshank in 1800. Carbon suboxide was discovered by Benjamin Brodie in 1873, by passing electric current through carbon dioxide. The fourth "classical" oxide, mellitic anhydride (C12O9), was apparently obtained by Liebig and Wöhler in 1830 in their study of mellite ("honeystone"), but was characterized only in 1913, by Meyer and Steiner.