Terpinene

Terpinenes
α-Terpinene	β-Terpinene
γ-Terpinene	δ-Terpinene; (terpinolene)
Names
	IUPAC names α: 4-Methyl-1-(1-methylethyl)-1,3-cyclohexadiene; β: 4-Methylene-1-(1-methylethyl)cyclohexene; γ: 4-Methyl-1-(1-methylethyl)-1,4-cyclohexadiene; δ: 1-Methyl-4-(propan-2-ylidene)cyclohex-1-ene
Identifiers
CAS Number	99-86-5 (α) ; 99-84-3 (β) ; 99-85-4 (γ) ; 586-62-9 (δ) ;
3D model (JSmol)	(α): Interactive image; (β): Interactive image; (γ): Interactive image; (δ): Interactive image;
ChEBI	CHEBI:59159 ;
ChemSpider	60205 ;
ECHA InfoCard	100.029.440
	InChI InChI=1S/C10H16/c1-8(2)10-6-4-9(3)5-7-10/h6,8H,3-5,7H2,1-2H3 Key: SCWPFSIZUZUCCE-UHFFFAOYSA-N ;
	SMILES (α): CC1=CC=C(C(C)C)CC1; (β): C=C1CC=C(C(C)C)CC1; (γ): CC1=CCC(C(C)C)=CC1; (δ): C/C(C)=C1CCC(C)=CC/1;
Properties
Chemical formula	C10H16
Molar mass	136.24 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 otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references

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

Biosynthesis of α-terpinene.^[2] "P" indicates a phosphate group, -PO₃²⁻

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.

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

Plants that produce terpinene

References

1 2 M. Eggersdorfer (2005). "Terpenes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a26_205.
↑ Dewick, P. M. (2009). Medicinal Natural Products: A Biosynthetic Approach. United Kingdom: John Wiley & Sons. pp. 187–197.
↑ 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. doi:10.1016/j.aca.2009.05.030. PMID 19576388.
↑ 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. PMID 15631509.
↑ Hillig, Karl W (2004-10). "A chemotaxonomic analysis of terpenoid variation in Cannabis". Biochemical Systematics and Ecology. 32 (10): 875–891. doi:10.1016/j.bse.2004.04.004. ISSN 0305-1978. Check date values in: |date= (help)

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[UllmannEgg-1] 1 2 M. Eggersdorfer (2005). "Terpenes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a26_205.

[2] Dewick, P. M. (2009). Medicinal Natural Products: A Biosynthetic Approach. United Kingdom: John Wiley & Sons. pp. 187–197.

[cceo-3] 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.

[unec-4] 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. doi:10.1016/j.aca.2009.05.030. PMID 19576388.

[aacc-5] 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. PMID 15631509.

[6] Hillig, Karl W (2004-10). "A chemotaxonomic analysis of terpenoid variation in Cannabis". Biochemical Systematics and Ecology. 32 (10): 875–891. doi:10.1016/j.bse.2004.04.004. ISSN 0305-1978. Check date values in: |date= (help)