<P> In chemistry, an organic compound is generally any chemical compound that contains carbon . Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known . Study of the properties and synthesis of organic compounds is the discipline known as organic chemistry . For historical reasons, a few classes of carbon - containing compounds (e.g., carbonates and cyanides), along with a handful of other exceptions (e.g., carbon dioxide), are not classified as organic compounds and are considered inorganic . No consensus exists among chemists on precisely which carbon - containing compounds are excluded, making the definition of an organic compound elusive . Although organic compounds only make up a small percentage of the Earth's crust, they are of central importance because all known life is based on organic compounds . Most synthetically produced organic compounds are ultimately derived from petrochemicals consisting mainly of hydrocarbons . </P> <P> For historical reasons discussed below, a few types of carbon - containing compounds, such as carbides, carbonates, simple oxides of carbon (for example, CO and CO), and cyanides are considered inorganic . Allotropes of carbon, such as diamond and graphite, are also excluded because they are simple substances composed of only a single element and therefore are not chemical compounds at all . </P> <P> Organic chemistry is the science concerned with all aspects of organic compounds . Organic synthesis is the methodology of their preparation . </P> <P> For many centuries, Western physicians and chemists believed in vitalism . This was the widespread conception that substances found in organic nature are created from the chemical elements by the action of a "vital force" or "life - force" (vis vitalis) that only living organisms possess . Vitalism taught that these "organic" compounds were fundamentally different from the "inorganic" compounds that could be obtained from the elements by chemical manipulations . </P>

Compounds containing c-c or c-h bonds formed by living things are often called