is a hydrocarbon lacking a
full complement of hydrogen atoms, and thus characterized by one or more
double or triple bonds between carbon atoms. Hydrocarbons having only one
double bond between adjacent carbon atoms in the molecule are called
olefins; those having two double bonds in the
molecule are diolefins. Hydrocarbons having
alternating single and double bonds between adjacent carbon atoms in a
benzene-ring configuration are called
aromatics. Hydrocarbons with a triple bond
between carbon atoms are called acetylenes.
Unsaturated hydrocarbons readily attract additional hydrogen, oxygen, or
other atoms, and are therefore highly reactive.
Also see saturated
hydrocarbon, hydrogenation.