Modelo del limoneno Alkenes are hydrocarbons that contain carbon-carbon double bonds. The word olefin is frequently used as a synonym.

Alkenes abound in nature. Ethene is a compound that controls plant growth, seed germination and fruit ripening.

α−Pinene is a fragrance obtained from pine trees. β-Carotene is a compound that contains 11 double bonds and is a precursor of vitamin A.