The terpinenes are a group of
isomeric hydrocarbons that are classified as
monoterpenes. They each have the same molecular formula and carbon framework, but they differ in the position of carbon-carbon double bonds. α-Terpinene has been isolated from
cardamom and
marjoram oils, and from other natural sources. β-Terpinene has no known natural source but has been prepared from
sabinene. γ-Terpinene and δ-terpinene (also known as terpinolene) have been isolated from a variety of plant sources. They are all colorless liquids with a turpentine-like odor.[1]
Production and uses
α-Terpinene is produced industrially by acid-catalyzed rearrangement of α-
pinene. It has perfume and flavoring properties but is mainly used to confer pleasant odor to industrial fluids. Hydrogenation gives the saturated derivative
p-menthane.[1]
Biosynthesis of α-terpinene
The biosynthesis of α-terpinene and other terpenoids starts with the isomerization of
geranyl pyrophosphate to
linalyl pyrophosphate (LPP). LPP then forms a resonance-stabilized cation by loss of the pyrophosphate group. Cyclization is then completed thanks to this more favorable stereochemistry of the LPP cation, yielding a terpinyl cation.[3] Finally, a 1,2-hydride shift via a
Wagner-Meerwein rearrangement produces the terpinen-4-yl cation. It is the loss of a hydrogen from this cation that generates α-terpinene.
^Li, Rong; Zi-Tao Jiang (2004). "Chemical composition of the essential oil of Cuminum cyminum L. from China". Flavour and Fragrance Journal. 19 (4): 311–313.
doi:
10.1002/ffj.1302.
^Wang, Lu; Wang, Z; Zhang, H; Li, X; Zhang, H; et al. (2009). "Ultrasonic nebulization extraction coupled with headspace single drop microextraction and gas chromatography–mass spectrometry for analysis of the essential oil in Cuminum cyminum L.". Analytica Chimica Acta. 647 (1): 72–77.
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2009AcAC..647...72W.
doi:
10.1016/j.aca.2009.05.030.
PMID19576388.
^Iacobellis, Nicola S.; Lo Cantore, P; Capasso, F; Senatore, F; et al. (2005). "Antibacterial Activity of Cuminum cyminum L. and Carum carvi L. Essential Oils". Journal of Agricultural and Food Chemistry. 53 (1): 57–61.
doi:
10.1021/jf0487351.
PMID15631509.