Compounds of carbon

Compounds of carbon are defined as chemical substances containing carbon. More compounds of carbon exist than any other chemical element except for hydrogen. Organic carbon compounds are far more numerous than inorganic carbon compounds. In general bonds of carbon with other elements are covalent bonds. Carbon is tetravalent but carbon free radicals and carbenes occur as short-lived intermediates. Ions of carbon are carbocations and carbanions are also short-lived. An important carbon property is catenation as the ability to form long carbon chains and rings. Compounds of carbon are defined as chemical substances containing carbon. More compounds of carbon exist than any other chemical element except for hydrogen. Organic carbon compounds are far more numerous than inorganic carbon compounds. In general bonds of carbon with other elements are covalent bonds. Carbon is tetravalent but carbon free radicals and carbenes occur as short-lived intermediates. Ions of carbon are carbocations and carbanions are also short-lived. An important carbon property is catenation as the ability to form long carbon chains and rings. The known inorganic chemistry of the allotropes of carbon (diamond, graphite, and the fullerenes) blossomed with the discovery of buckminsterfullerene in 1985, as additional fullerenes and their various derivatives were discovered. One such class of derivatives is inclusion compounds, in which an ion is enclosed by the all-carbon shell of the fullerene. This inclusion is denoted by the '@' symbol in endohedral fullerenes. For example, an ion consisting of a lithium ion trapped within buckminsterfullerene would be denoted Li+@C60. As with any other ionic compound, this complex ion could in principle pair with a counterion to form a salt. Other elements are also incorporated in so-called graphite intercalation compounds. Carbides are binary compounds of carbon with an element that is less electronegative than it. The most important areAl4C3,B4C,CaC2,Fe3C,HfC,SiC,TaC,TiC, andWC. It was once thought that organic compounds could only be created by living organisms. Over time, however, scientists learned how to synthesize organic compounds in the lab. The number of organic compounds is immense and the known number of defined compounds is close to 10 million. However, an indefinitely large number of such compounds are theoretically possible. By definition, an organic compound must contain at least one atom of carbon, but this criterion is not generally regarded as sufficient. Indeed, the distinction between organic and inorganic compounds is ultimately a matter of convention, and there are several compounds that have been classified either way, such as:COCl2,CSCl2,CS(NH2)2,CO(NH2)2.With carbon bonded to metals the field of organic chemistry crosses over into organometallic chemistry. There is a rich variety of carbon chemistry that does not fall within the realm of organic chemistry and is thus called inorganic carbon chemistry. There are many oxides of carbon (oxocarbons), of which the most common are carbon dioxide (CO2) and carbon monoxide (CO). Other less known oxides include carbon suboxide (C3O2) and mellitic anhydride (C12O9). 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–C≡C–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 areAg2CO3,BaCO3,CaCO3,CdCO3,Ce2(CO3)3,CoCO3,Cs2CO3,CuCO3,FeCO3,K2CO3,La2(CO3)3,Li2CO3,MgCO3,MnCO3,(NH4)2CO3,Na2CO3,NiCO3,PbCO3,SrCO3, andZnCO3. The most important bicarbonates include NH4HCO3,Ca(HCO3)2,KHCO3, andNaHCO3.