Aliphatic hydrocarbons have the principal carbon atoms arranged in chains. They are further divided into the paraffin, olefin, and acetylenic series. Paraffins, or alkanes, include the greatest number of hydrocarbon compounds. Methane is the first member of the series. Others include ethane and propane.
Paraffins react by substitution.
Hydrogen atoms are replaced by other atoms or groups of atoms, such as halogens or hydroxyls. Olefins, or alkenes, have at least one double bond between two carbon atoms. Ethylene is the first member. Olefins react primarily by addition of molecules such as water, oxygen, and halogens. Acetylenes, or alkynes, have at least one triple bond between two carbon atoms.