ALKANES, ALKENES & TERPENES [home] [topic page]
Essential Oils are chemicals derived from plant components, be they fruits, stems or leaves.
The molecules are carbon based and are often alkanes or alkenes.
ALKANES are hydrocarbons with only single covalent bonds between carbon atoms.
ALKENES have one or more double covalent bond between the carbon atoms.
The alkenes of plants are often derived from one particular alkene, isoprene, 2-methyl-1,3-butadiene.
Isoprene turns out to be given off by vegetation, especially on hot days, and contributes strongly to the bluish haze that envelops many forest areas when viewed from afar. ( The blue light of the Sun is strongly scattered by these molecules. )
This family of alkenes is called the TERPENE family. It is huge. The word is derived from the oil "turpentine" or "terpentine" - its alternative earlier spelling, which in turn is from the terebinth tree. Turpentine is alpha - pinene.
To make terpenes from isoprene, hydrogen displacement may take place or a double bond may break to give an addition reaction.
Terpenes with 2 units of isoprene are monoterpenes, C10H16 , with three units are sequiterpenes, C15H24 and so on,
These carbohydrates may also be in "cyclo-" form meaning that they form a ring of carbon atoms.
Further structures are the addition of side groups
hydroxyl groups in which case they are alcohols and phenols.
carboxylic
groups when they become acids
ketones
aldehydes
ethers
These are still included in the terpene family.
