TerpenesTerpenes

Terpenes are a class of molecules that typically contain either ten or fifteen carbon atoms built from a five-carbon building block called isoprene. It is important to note these molecules are volatile —they tend to evaporate relatively easily.

Many terpenes are hydrocarbons, but oxygen- containing compounds such as alcohols, aldehydes or ketones are also found. These derivatives are frequently named terpenoids. Their building block is the hydrocarbon isoprene, CH 2 =C(CH 3 )-CH=CH 2. Terpene hydrocarbons therefore have molecular formulas (C5H8)n. The systematic name of isoprene 2-methyl-1,3-butadiene.

A rational classification of the terpenes has been established based upon the number of isoprene (or isopentane) units incorporated in the basic molecular skeleton: TerpenesIsoprene UnitsCarbon Atoms Monoterpenes210 Sesquiterpenes315 Diterpenes420 Sesterpenes525 Triterpenes630 Tetraterpenes840 Rubber>100>500

In plants, terpenes are typically found as a component of the essential oils. The name of this fluid suggests an important characteristic of this class of molecules. If humans have found these oils important enough to refer to them as essential, there is a reasonable chance that they have useful properties.

Isoprenoid units are also found within the framework of other natural molecules. Thus, indole alkaloids, several quinones (vitamin K), alcohols (vitamin E, vitamin A formed from b-carotene), phenols, isoprenoid alcohols (also known as terpenols or polyprenols) also contain terpenoid fragments.

Examples of terpenes: