There are also numerous unstable or elusive oxides, such as dicarbon monoxide (C2O), oxalic anhydride (C2O4), and carbon trioxide (CO3).
There are several oxocarbon anions, negative ions that consist solely of oxygen and carbon. The most common are the carbonate (CO32) and oxalate (C2O42). The corresponding acids are the highly unstable carbonic acid (H2CO3) and the quite stable oxalic acid (H2C2O4), respectively. These anions can be partially deprotonated to give the bicarbonate (HCO3) and hydrogenoxalate (HC2O4). Other more exotic carbon–oxygen anions exist, such as acetylenedicarboxylate (O2C–CC–CO22), mellitate (C12O96), squarate (C4O42), and rhodizonate (C6O62). The anhydrides of some of these acids are oxides of carbon; carbon dioxide, for instance, can be seen as the anhydride of carbonic acid.
Some important carbonates are Ag2CO3, BaCO3, CaCO3, CdCO3, Ce2(CO3)3, CoCO3, Cs2CO3, CuCO3, FeCO3, K2CO3, La2(CO3)3, Li2CO3, MgCO3, MnCO3, (NH4)2CO3, Na2CO3, NiCO3, PbCO3, SrCO3, and ZnCO3.
The most important bicarbonates include NH4HCO3, Ca(HCO3)3, KHCO3, and NaHCO3.
The most important oxalates include Ag2C2O4, BaC2O4, CaC2O4, Ce2(C2O4)3, K2C2O4, and Na2C2O4.
Carbonyls are coordination complexes between transition metals and carbonyl ligands. Metal carbonyls are complexes that are formed with the neutral ligand CO. These complexes are covalent.
Carbonyl. A compound containing a carbonyl group (C=O) In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O.
It is common to several classes of organic compounds, as part of many larger functional groups. A compound containing a carbonyl group is often referred to as a carbonyl compound. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e.g. nickel carbonyl). The remainder of this article concerns itself with the organic chemistry definition of carbonyl, where carbon and oxygen share a double bond. Carbonyl compounds A carbonyl group characterizes the following types of compounds: Note that the most specific labels are usually employed. Oxocarbon anion. 2D diagram of mellitateC 12O6− 12, one of the oxocarbon anions.
Black circles are carbon atoms, red circles are oxygen atoms. Each blue halo represents one half of a negative charge. In chemistry, an oxocarbon anion is a negative ion consisting solely of carbon and oxygen atoms, and therefore having the general formula CxOyn− for some integers x, y, and n. The most common oxocarbon anions are carbonate, CO32−, and oxalate, C2O42−. There is however a large number of stable anions in this class, including several ones that have research or industrial use. Distributed charges and resonances so that each oxygen has the same negative charge equivalent to 2/3 of one electron, and each C–O bond has the same average valence of 4/3. Similarly, in a deprotonated carboxyl group –CO– 2, each oxygen is often assumed to have a charge of −1/2 and each C–O bond to have valence 3/2, so the two oxygens are equivalent. Related compounds Oxocarbon acids Neutralized species See also
Carbon trioxide. The Cs, D3h, and C2v isomers of carbon trioxide.
Carbon trioxide (CO3) is an unstable oxide of carbon (an oxocarbon). Three possible isomers of carbon trioxide, with molecular symmetry point groups Cs, D3h, and C2v, have been most studied by theoretical methods, and the C2v state has been shown to be the ground state of the molecule. Carbon trioxide should not be confused with the stable carbonate ion (CO32−).
Another reported method is photolysis of ozone O3 dissolved in liquid CO2, or in CO2/SF6 mixtures at -45 °C, irradiated with light of 2537 Å. The formation of CO3 is inferred but it appears to decay spontaneously by the route 2CO3 → 2CO2 + O2 with a lifetime much shorter than 1 minute. Oxalic anhydride. Oxalic anhydride or ethanedioic anhydride, also called oxiranedione, is a hypothetical organic compound with the formula C2O3, which can be viewed as the anhydride of oxalic acid or the two-fold ketone of ethylene oxide.
It is an oxide of carbon (an oxocarbon). It has been conjectured to be a fleeting intermediate in the thermal decomposition of certain oxalates and certain chemoluminescent reactions of oxalyl chloride. References Dicarbon monoxide. Occurrence Dicarbon monoxide is a product of the photolysis of carbon suboxide: It is stable enough to observe reactions with NO and NO2. Called ketenylidene in organometallic chemistry, it is a ligand observed in metal carbonyl clusters, e.g.
[OC2Co3(CO)9]+. Ketenylidenes are proposed as intermediates in the chain growth mechanism of the Fischer-Tropsch Process, which converts carbon monoxide and hydrogen to hydrocarbon fuels. The organophosphorus compound (C6H5)3PCCO (CAS# 15596-07-3) contains the C2O functionality. References Jump up ^ Frenking, Gernot; Tonner, Ralf "Divalent carbon(0) compounds" Pure and Applied Chemistry 2009, vol. 81, pp. 597-614. doi:10.1351/PAC-CON-08-11-03Jump up ^ Bayes, K. (1961). Mellitic anhydride. Mellitic anhydride, the anhydride of mellitic acid, is an organic compound with the formula C12O9.
Mellitic anhydride is an oxide of carbon (oxocarbon), like CO2, CO, and C3O2. It is a white sublimable solid, apparently obtained by Liebig and Wöhler in 1830 in their study of mellite ("honey stone"); they assigned it the formula C4O3. The substance was properly characterized in 1913 by H. Meyer and K. Steiner. It retains the aromatic character of the benzene ring. ^ Jump up to: a b c d e f "NIOSH Pocket Guide to Chemical Hazards #0635". Carbon suboxide. Carbon suboxide, or tricarbon dioxide, is an oxide of carbon with chemical formula C3O2 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=Cn=O, which also includes carbon dioxide (CO2) and pentacarbon dioxide (C5O2). The substance was discovered in 1873 by Benjamin Brodie by subjecting carbon monoxide to an electric current. Carbon monoxide. Carbon monoxide (CO) is a colorless, odorless, and tasteless gas that is slightly less dense than air.
It is toxic to humans when encountered in concentrations above about 35 ppm, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal biological functions. In the atmosphere, it is spatially variable and short lived, having a role in the formation of ground-level ozone. Carbon monoxide consists of one carbon atom and one oxygen atom, connected by a triple bond that consists of two covalent bonds as well as one dative covalent bond. It is the simplest oxocarbon and is isoelectronic with the cyanide anion, the nitrosonium cation and molecular nitrogen. In coordination complexes the carbon monoxide ligand is called carbonyl. In biology, carbon monoxide is naturally produced by the action of heme oxygenase 1 and 2 on the heme from hemoglobin breakdown. History Molecular properties Carbon dioxide. Atmospheric carbon dioxide is the primary source of carbon in life on Earth and its concentration in Earth's pre-industrial atmosphere since late in the Precambrian was regulated by photosynthetic organisms and geological phenomena.
As part of the carbon cycle, plants, algae, and cyanobacteria use light energy to photosynthesize carbohydrate from carbon dioxide and water, with oxygen produced as a waste product. Carbon dioxide is produced by plants during respiration. Carbon dioxide (CO2) is a product of respiration of all aerobic organisms.
It is returned to water via the gills of fish and to the air via the lungs of air-breathing land animals, including humans. Oxocarbon. 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 (CO2).
Many other stable or metastable oxides of carbon are known, but they are rarely encountered, such as carbon suboxide (C3O2 or O=C=C=C=O) and mellitic anhydride (C12O9). While textbooks will often list only the first three, and rarely the fourth, a large number of 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. The inventory of oxocarbons appears to be steadily growing.