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| Names | |||
|---|---|---|---|
| IUPAC name (1S,5S)-2,6,6-Trimethylbicyclo[3.1.1]hept-2-ene ((−)-α-Pinene) | |||
| Identifiers | |||
3D model (JSmol) | |||
| ChEBI |
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| ChemSpider |
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| ECHA InfoCard | 100.029.161 | ||
| EC Number |
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| KEGG |
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| RTECS number |
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| UNII |
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| UN number | 2368 | ||
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| Properties | |||
| C10H16 | |||
| Molar mass | 136.238 g·mol−1 | ||
| Appearance | Clear colorless liquid | ||
| Density | 0.858 g/mL (liquid at 20 °C) | ||
| Melting point | −62.80 °C; −81.04 °F; 210.35 K[1] | ||
| Boiling point | 155 °C (311 °F; 428 K)[1] | ||
| Very low | |||
| Solubility | Insoluble inchloroform,diethyl ether | ||
| Solubility inacetic acid | Miscible | ||
| Solubility inethanol | Miscible | ||
| Solubility inacetone | Miscible | ||
| Vapor pressure | 0.5 kPa | ||
Chiral rotation ([α]D) | −50.7° (1S,5S-Pinene) | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | Flammable | ||
| GHS labelling: | |||
   | |||
| Danger | |||
| H226,H302,H304,H315,H317,H410 | |||
| P210,P233,P240,P241,P242,P243,P261,P264,P270,P272,P273,P280,P301+P310,P301+P312,P302+P352,P303+P361+P353,P321,P330,P331,P332+P313,P333+P313,P362,P363,P370+P378,P391,P403+P235,P405,P501 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | 33 °C (91 °F; 306 K) | ||
| 255 °C (491 °F; 528 K) | |||
| Explosive limits | 0.8% v/v (lower) 6% v/v (upper) | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 300-2000 mg/kg (rat, oral) > 5 g/kg (rabbit, dermal) | ||
LC50 (median concentration) | 625 ppm/min (rat) | ||
| Safety data sheet (SDS) | Fisher Scientific | ||
| Related compounds | |||
Related alkene | β-pinene,camphene,3-carene,limonene | ||
Related compounds | borneol,camphor,terpineol | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
α-Pinene is anorganic compound of theterpene class. It is one of the twoisomers ofpinene, the other beingβ-pinene.[2] Analkene, it contains a strainedfour-membered ring. It is found in the oils of many species ofconiferous trees, notablyPinus andPicea species. It is also found in theessential oil ofrosemary (Rosmarinus officinalis) andSatureja myrtifolia (also known asZoufa in some regions).[3][4] Bothenantiomers are known in nature; (1S,5S)- or (−)-α-pinene is more common in European pines, whereas the (1R,5R)- or (+)-α-isomer is more common in North America. The enantiomers'racemic mixture is present in some oils such aseucalyptus oil andorange peel oil.
Commercially important derivatives of α-pinene arelinalool,geraniol,nerol, α-terpineol, andcamphene.[5]
α-Pinene1 demonstrates reactivity arising from the presence of the four-membered ring adjacent to the alkene.[6] The compound is prone to skeletal rearrangements such as theWagner–Meerwein rearrangement. Acids typically lead to rearranged products. With concentratedsulfuric acid andethanol the major products areterpineol2 and its ethylether3, while glacialacetic acid gives the correspondingacetate4. With dilute acids,terpin hydrate5 becomes the major product.
With onemolar equivalent ofanhydrous HCl, the simple addition product6a can be formed at low temperature in the presence ofdiethyl ether, but it is very unstable. At normal temperatures, or if no ether is present, the major product isbornyl chloride6b, along with a small amount offenchyl chloride6c.[7] For many years6b (also called "artificialcamphor") was referred to as "pinene hydrochloride", until it was confirmed as identical with bornyl chloride made fromcamphene. If more HCl is used,achiral7 (dipentene hydrochloride) is the major product along with some6b.Nitrosyl chloride followed by base leads to theoxime 8 which can be reduced to "pinylamine"9. Both8 and9 are stable compounds containing an intact four-membered ring, and these compounds helped greatly in identifying this important component of the pinene skeleton.[8]
Under aerobic oxidation conditions, the main oxidation products arepinene oxide,verbenyl hydroperoxide,verbenol andverbenone.[9]
Monoterpenes, of which α-pinene is one of the principal species, are emitted in substantial amounts by vegetation, and these emissions are affected by temperature and light intensity. In the atmosphere α-pinene undergoes reactions withozone, thehydroxyl radical or theNO3 radical,[10][full citation needed] leading to low-volatility species which partly condense on existing aerosols, thereby generating secondary organic aerosols. This has been shown in numerous laboratory experiments for the mono- andsesquiterpenes.[11][12] Products of α-pinene which have been identified explicitly arepinonaldehyde,norpinonaldehyde,pinic acid,pinonic acid andpinalic acid.[citation needed]
α-Pinene is highlybioavailable, with 60% human pulmonary uptake and rapid metabolism or redistribution.[13] α-Pinene is ananti-inflammatory viaPGE1,[13] and is likelyantimicrobial.[14] It exhibits activity as anacetylcholinesterase inhibitor, aiding memory.[13] Likeborneol,verbenol andpinocarveol (−)-α-pinene is apositive modulator ofGABAA receptors. It acts at thebenzodiazepinebinding site.[15]
α-Pinene forms the biosynthetic base forCB2 ligands, such asHU-308.[13]
α-Pinene is one of the manyterpenes andterpenoids found incannabis plants.[16] These compounds are also present in significant levels in the finished, dried cannabis flower preparation commonly known asmarijuana.[17] It is widely theorized by scientists and cannabis experts alike that these terpenes and terpenoids contribute significantly to the unique "character" or "personality" of each marijuana strain's unique effects.[18] α-Pinene in particular is thought to reduce the memory deficits commonly reported as a side-effect of THC consumption.[citation needed] It likely demonstrates this activity due to its action as anacetylcholinesterase inhibitor, a class of compounds which are known to aid memory and increase alertness.[19][additional citation(s) needed]
α-Pinene also contributes significantly to many of the varied, distinct, and unique odor profiles of the multitude of marijuana strains, varieties andcultivars.[20]
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