Organic compounds are a subclass of chemical compounds of carbon. Little consensus exists among chemists on the exact definition of organic compound; the only universally accepted definition is the quasi-tautological "organic compounds are the subject matter of organic chemistry".
Generally, any large chemical compound containing a carbon–hydrogen or carbon–carbon bond is accepted as an organic compound. Thus alkanes (e.g. ethane, CH3−CH3) and their derivatives are typically considered organic. For historical and disciplinary reasons, small molecules containing carbon are generally not accepted: cyanide ion (CN), hydrogen cyanide (HCN), chloroformic acid (ClCO2H), carbon dioxide (CO2), and carbonate ion (CO2−3) may all be excluded.
