Alkenes: Occurence and Importance in Nature
In nature, alkenes most frequently are part of large ring systems. Terpenes which are the primary constituents ofpresumably constitute the most important compound class among these ring systems.
Conjugated polyenes are, for example, vitamin A (retinal) and β-carotene (provitamin A).
In this context it is of interest to mention that the vision process is based on a light induced cis-trans isomerization of protein-bound retinol.
polymerization of isoprene (2-methyl-1,3-butadiene).is a polyene produced from the milky sap of the rubber tree. Formally, this unsaturated hydrocarbon is derived by
Ethene, the most simple alkene, can also be found in nature. As a plant hormone, it effects the ripening of fruits. Fruits, e.g. kiwis, which either have to be transported over long distances or have to be stored for longer periods of time are harvested early and stored at low temperatures and high concentration. Subsequently, ripening is initiated by treating the fruits with gaseous ethene.