|CAS number||(α) , (β) , (γ) , (δ)|
|Jmol-3D images||Image 1
|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 (77 °F), 100 kPa)|
|(what is: / ?)|
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
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