Terpinene

Terpinenes

α-Terpinene
β-Terpinene

γ-Terpinene
δ-Terpinene
(terpinolene)
Identifiers
CAS number 99-86-5 (α) Y, 99-84-3 (β) Y, 99-85-4 (γ) Y, 586-62-9 (δ) Y
Jmol-3D images Image 1
Image 2
Image 3
Image 4
Properties
Molecular formula C10H16
Molar mass 136.23 g mol−1
Density α: 0.8375 g/cm3
β: 0.838 g/cm3
γ: 0.853 g/cm3
Melting point

α: 60-61 °C
Boiling point

α: 173.5-174.8 °C
β: 173-174 °C
γ: 183 °C
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

The terpinenes are a group of isomeric hydrocarbons that are classified as terpenes. 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 synthetically from sabinene. γ-Terpinene and δ-terpinene (also known as terpinolene) are natural and have been isolated from a variety of plant sources.

Biosynthesis of α-terpinene

The biosynthesis of α-terpinene and other terpenoids occurs via the mevalonate pathway because its starting reactant, dimethylallyl pyrophosphate (DMAPP), is derived from mevalonic acid. Though α-terpinene is commonly considered a perfume and flavoring chemical and therefore used in the cosmetics and food industries, its use both in the pharmaceutical and electronics semi-conductor manufacturing industries have also proven to be valuable.

Geranyl pyrophosphate (GPP) is produced from the reaction of a resonance-stable allylic cation, formed from the loss of the diphosphate group from DMAPP, and isopentenyl pyrophosphate (IPP), and a subsequent the loss of a proton. GPP then loses the diphosphate group to form the resonance-stable geranyl cation. The reintroduction of the diphosphate group to the cation produces GPP isomer, known as linalyl pyrophosphate (LPP). LPP then forms a resonance-stable cation by losing its diphosphate group. Cyclization is then completed thanks to this more favorable stereochemistry of the LPP cation, now yielding the menthyl/α-terpinyl cation. 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.

List of the plants that contain one of the chemicals

References

  1. ^ Dewick, P. M. (2009). Medicinal Natural Products: A Biosynthetic Approach. United Kingdom: John Wiley & Sons. 187-197
  2. ^ 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. 
  3. ^ Wang, Lu et al.; Wang, Z; Zhang, H; Li, X; Zhang, H (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. doi:10.1016/j.aca.2009.05.030. PMID 19576388. 
  4. ^ Iacobellis, Nicola S. et al.; Lo Cantore, P; Capasso, F; Senatore, F (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. PMID 15631509.