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| Names | |||
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| 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 | |||
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3D model (JSmol) |
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| ChemSpider | |||
| ECHA InfoCard | 100.029.440 | ||
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| Properties | |||
| C10H16 | |||
| Molar mass | 136.238 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 theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Theterpinenes are a group ofisomeric hydrocarbons that are classified asmonoterpenes. 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 fromcardamom andmarjoram oils, and from other natural sources. β-Terpinene has no known natural source but has been prepared fromsabinene. γ-Terpinene and δ-terpinene (also known asterpinolene) have been isolated from a variety of plant sources. They are all colorless liquids with a turpentine-like odor.[1]
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 derivativep-menthane.[1]
The biosynthesis of α-terpinene and other terpenoids starts with the isomerization ofgeranyl pyrophosphate tolinalyl 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 aWagner-Meerwein rearrangement produces the terpinen-4-yl cation. It is the loss of a hydrogen from this cation that generates α-terpinene.
