An organic chemical compound of hydrogen and carbon in the gaseous, liquid, or solid phase: The molecular structure of hydrocarbon compounds varies from the simplest (methane, a constituent of natural gas) to the very heavy and very complex.

Hydrocarbons are compounds composed of carbon and hydrogen.

When they are chlorinated, chlorine is substituted for one or more of the hydrogens. Low molecular weight chlorinated hydrocarbons; such as, carbon tetrachloride, are highly volatile and relatively unstable in the environment.