Hydrocarbons
. Hydrocarbons, family of organic compounds, composed entirely of carbon and hydrogen. They are the organic compounds of simplest composition and may be considered the parent substances from which all other organic compounds are derived. The hydrocarbons are conveniently classified into two major groups, open-chain and cyclic. In open-chain compounds containing more than one carbon atom, the carbon atoms are attached to each other to form an open chain; the chain may carry one or more side branches. In cyclic compounds the carbon atoms form one or more closed rings. The two major groups are subdivided according to chemical behavior into saturated and unsaturated compounds. OPEN-CHAIN HYDROCARBONS The saturated open-chain hydrocarbons form a homologous series called the paraffin (Latin parum affinis, “little affinity”) series or the alkane series. Among the members of the series are methane, ethane, propane, and butane. All the members of the series are unreactive; that is, they do not