View source for Α-Pinene

{{DISPLAYTITLE:α-Pinene}}
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 477319613
| Name = α-Pinene
| ImageFile = Alpha-Pinene Isomers.svg
| ImageSize = 220px
| ImageFileL1 = (−)-alpha-pinene-3D-balls.png
| ImageCaptionL1 = (+)-α-pinene
| ImageFileR1 = (1S)-(−)-alpha-pinene-from-xtal-3D-balls.png
| ImageCaptionR1 = (−)-α-pinene
| IUPACName = (1''S'',5''S'')-2,6,6-Trimethylbicyclo[3.1.1]hept-2-ene ((−)-α-Pinene)
| OtherNames =
|Section1={{Chembox Identifiers
| index1_label = (+)
| index2_label = (−)
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = JPF3YI7O34
| UNII_Comment = unspecified
| UNII1_Ref = {{fdacite|correct|FDA}}
| UNII1 = H6CM4TWH1W
| UNII2_Ref = {{fdacite|correct|FDA}}
| UNII2 = TZR3GM95PR

| ChEBI_Ref = {{ebicite|changed|EBI}}
| ChEBI = 36740
| ChEBI_Comment = unspecified
| ChEBI2_Ref = {{ebicite|changed|EBI}}
| ChEBI2 = 28660
| ChEBI1_Ref = {{ebicite|changed|EBI}}
| ChEBI1= 28261
| EC_number2 = 232-077-3
| SMILES = C\1=C(\[C@@H]2C[C@H](C/1)C2(C)C)C
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = C06308
| InChI = 1/C10H16/c1-7-4-5-8-6-9(7)10(8,2)3/h4,8-9H,5-6H2,1-3H3/t8-,9-/m0/s1
| InChIKey = GRWFGVWFFZKLTI-IUCAKERBBG
| PubChem = 440968
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C10H16/c1-7-4-5-8-6-9(7)10(8,2)3/h4,8-9H,5-6H2,1-3H3/t8-,9-/m0/s1
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = GRWFGVWFFZKLTI-IUCAKERBSA-N
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 80-56-8
| CASNo_Comment = unspecified
| CASNo1_Ref = {{cascite|correct|CAS}}
| CASNo1 = 7785-70-8
| CASNo2_Ref = {{cascite|correct|CAS}}
| CASNo2 = 7785-26-4
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID=389795
| UNNumber = 2368
| RTECS = DT7000000 (unspec. isomer)
 }}
|Section2={{Chembox Properties
| C=10 | H=16
| Appearance = Clear colorless liquid
| Density = 0.858{{nbsp}}g/mL (liquid at 20{{nbsp}}°C)
| Solubility = Very low
| Solubility1 = Miscible
| Solvent1 = acetic acid
| Solubility2 = Miscible
| Solvent2 = ethanol
| Solubility3 = Miscible
| Solvent3 = acetone
| SolubleOther = Insoluble in [[chloroform]], [[diethyl ether]]
| MeltingPtK = 210.35
| MeltingPt_ref = <ref name="auto">{{cite web |url=http://webbook.nist.gov/cgi/cbook.cgi?ID=80-56-8&Units=SI&cTG=on&cIR=on&cTC=on&cTZ=on&cTP=on&cMS=on&cTR=on&cUV=on&cIE=on&cGC=on&cIC=on&cES=on&cDI=on&cSO=on |title=α-Pinene |access-date=2018-01-29 |url-status=live |archive-url=https://web.archive.org/web/20180130091652/http://webbook.nist.gov/cgi/cbook.cgi?ID=80-56-8&Units=SI&cTG=on&cIR=on&cTC=on&cTZ=on&cTP=on&cMS=on&cTR=on&cUV=on&cIE=on&cGC=on&cIC=on&cES=on&cDI=on&cSO=on |archive-date=2018-01-30 }}</ref>
| BoilingPtC = 155
| BoilingPt_ref = <ref name="auto"/>
| VaporPressure = 0.5 kPa
| SpecRotation = −50.7° (1''S'',5''S''-Pinene)
 }}
|Section7={{Chembox Hazards
| MainHazards = Flammable
| FlashPtC = 33
| AutoignitionPtC = 255
| NFPA-H = 3
| NFPA-F = 3
| NFPA-R = 0
| GHSPictograms = {{GHS02}}{{GHS07}}{{GHS08}}
| GHSSignalWord = Danger
| ExploLimits = 0.8% v/v (lower)<br>6% v/v (upper)
| HPhrases = {{H-phrases|226|302|304|315|317|410}}
| PPhrases = {{P-phrases|210|233|240|241|242|243|261|264|270|272|273|280|301+310|301+312|302+352|303+361+353|321|330|331|332+313|333+313|362|363|370+378|391|403+235|405|501}}
| LD50 = 300-2000 mg/kg (rat, oral)<br>> 5 g/kg (rabbit, dermal)
| LC50 = 625 ppm/min (rat)
| ExternalSDS = [https://www.fishersci.com/store/msds?partNumber=AC131270050&productDescription=ALPHA-PINENE+5ML&vendorId=VN00032119&countryCode=US&language=en Fisher Scientific]
 }}

|Section8={{Chembox Related
| OtherFunction_label = alkene
| OtherFunction = [[Beta-Pinene|β-pinene]], [[camphene]], [[3-carene]], [[limonene]]
| OtherCompounds = [[borneol]], [[camphor]], [[terpineol]]
 }}
}}

'''α-Pinene''' is an [[organic compound]] of the [[terpene]] class.  It is one of the two [[isomer]]s of [[pinene]], the other being [[beta-Pinene|β-pinene]].<ref>{{cite book|last=Simonsen|first=J. L.|date=1957|title=The Terpenes|edition=2nd|volume=2|location=Cambridge|publisher=Cambridge University Press|pages=105–191}}</ref> An [[alkene]], it contains a strained [[Cyclobutane|four-membered ring]]. It is found in the oils of many species of [[Pinophyta|coniferous]] trees, notably [[pine|''Pinus'']] and ''[[Picea]]'' species. It is also found in the [[essential oil]] of [[rosemary]] (''[[Rosmarinus]] officinalis'') and ''[[Satureja]] myrtifolia'' (also known as ''Zoufa'' in some regions).<ref>{{cite book|title=PDR for Herbal Medicine|location=Montvale, NJ|publisher=Medical Economics Company|page=1100}}</ref><ref>{{Cite journal|last1=Zebib|first1=Bachar|last2=Beyrouthy|first2=Marc El|last3=Sarfi|first3=Carl|last4=Merah|first4=Othmane|date=2015-04-16|title=Chemical Composition of the Essential Oil of ''Satureja myrtifolia'' (Boiss. & Hohen.) from Lebanon|url=https://www.researchgate.net/publication/275157301|journal=Journal of Essential Oil-bearing Plants |volume=18|issue=1|doi=10.1080/0972060X.2014.890075|issn=0972-060X|pages=248–254|s2cid=95564601|url-status=live|archive-url=https://web.archive.org/web/20160804182218/https://www.researchgate.net/publication/275157301_Chemical_Composition_of_the_Essential_Oil_of_Satureja_myrtifolia_Boiss_Hohen_from_Lebanon|archive-date=2016-08-04}}</ref> Both [[enantiomer]]s are known in nature; (1''S'',5''S'')- or (−)-α-pinene is more common in European pines, whereas the (1''R'',5''R'')- or (+)-α-isomer is more common in North America. The enantiomers' [[racemic mixture]] is present in some oils such as [[eucalyptus oil]] and [[orange peel oil]].

== Reactivity ==
:[[Image:alphaPinene rxns.png|450px|Some general reactions of α-pinene]]
Commercially important derivatives of α-pinene are [[linalool]], [[geraniol]], [[nerol]], α-[[terpineol]], and [[camphene]].<ref>{{cite book |doi=10.1002/0471238961.2005181602120504.a01.pub2|chapter=Terpenoids |title=Kirk-Othmer Encyclopedia of Chemical Technology |year=2006 |last1=Sell |first1=Charles S. |isbn=0471238961 }}</ref>

α-Pinene '''1''' demonstrates reactivity arising from the presence of the four-membered ring adjacent to the alkene.<ref>{{cite video|first1=George|last1=Gilbert|first2=Jerrold&nbsp;J.|last2=Jacobsen|first3=Kelly|last3=Houston&nbsp;Jetzer|first4=David|last4=Phillips|orig-date=29 Nov 2013|year=2022|title=Ring Strain - Demonstration|url=https://www.chemedx.org/video/ring-strain-demonstration|type=web video|publisher=American Chemical Society, Division of Chemical Education|via=ChemEdX}}</ref> The compound is prone to skeletal rearrangements such as the [[Wagner–Meerwein rearrangement]]. Acids typically lead to rearranged products. With concentrated [[sulfuric acid]] and [[ethanol]] the major products are [[terpineol]] '''2''' and its ethyl [[ether]] '''3''', while glacial [[acetic acid]] gives the corresponding [[acetate]] '''4'''. With dilute acids, [[terpin hydrate]] '''5''' becomes the major product.

With one [[mole (unit)|molar]] equivalent of [[Hydrogen chloride|anhydrous HCl]], the simple addition product '''6a''' can be formed at low temperature in the presence of [[diethyl ether]], but it is very unstable. At normal temperatures, or if no ether is present, the major product is [[bornyl chloride]] '''6b''', along with a small amount of [[fenchyl chloride]] '''6c'''.<ref>{{cite book |last1=Richter |first1=G.H. |title=Textbook of Organic Chemistry |date=1952 |publisher=John Wiley & Sons |location=New York, NY |pages=663–668 |edition=3rd |url=https://babel.hathitrust.org/cgi/pt?id=mdp.39015003707661&seq=7}}</ref> For many years '''6b''' (also called "artificial [[camphor]]") was referred to as "pinene hydrochloride", until it was confirmed as identical with bornyl chloride made from [[camphene]]. If more HCl is used, [[:Wiktionary:achiral|achiral]] '''7''' ([[dipentene]] hydrochloride) is the major product along with some '''6b'''. [[Nitrosyl chloride]] followed by base leads to the [[oxime]] 8 which can be reduced to "pinylamine" '''9'''. Both '''8''' and '''9''' are stable compounds containing an intact four-membered ring, and these compounds helped greatly in identifying this important component of the pinene skeleton.<ref>{{cite journal | doi = 10.1002/hlca.19210040161 | title = Zur Kenntnis des Pinens. III. Konstitution des Nitrosopinens und seiner Umwandlungsprodukte | trans-title = On the science of pinene. III. Constitution of nitrosopinene and its transformation products | year = 1921 | last1 = Ružička | first1 = L. | journal = Helvetica Chimica Acta | volume = 4 | pages = 566–574 | last2 = Trebler | first2 = H. | url = https://zenodo.org/record/1426813 | author-link = Lavoslav Ružička }}</ref>

Under aerobic oxidation conditions, the main oxidation products are [[pinene oxide]], [[verbenyl hydroperoxide]], [[verbenol]] and [[verbenone]].<ref>
{{cite journal|first1=U.|last1=Neuenschwander|journal=ChemSusChem|title=Mechanism of the Aerobic Oxidation of α-Pinene |volume=3|issue=1|year=2010|pages=75–84|language=de|doi=10.1002/cssc.200900228|pmid=20017184|doi-access=free|bibcode=2010ChSCh...3...75N }}
</ref>

{{clear left}}

== Atmospheric role ==
[[Monoterpene]]s, 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 with [[ozone]], the [[hydroxyl radical]] or the [[nitrate radical|NO<sub>3</sub> radical]],<ref>IUPAC Subcommittee on Gas Kinetic Data Evaluation</ref>{{full citation needed|date=July 2019}} 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- and [[sesquiterpene]]s.<ref>{{cite journal |last1=Odum |first1=J. R. |last2=Hoffmann |first2=T. |last3=Bowman |first3=F. |last4=Collins |first4=D. |last5=Flagan |first5=R. C. |last6=Seinfeld |first6=J. H. | year = 1996 | title = Gas/particle partitioning and secondary organic aerosol yields | journal = Environmental Science and Technology | volume = 30 | pages = 2580–2585 | doi = 10.1021/es950943+ | issue = 8|bibcode=1996EnST...30.2580O }}</ref><ref>{{cite journal |first1=N. M. |last1=Donahue |first2=K. M. |last2=Henry |first3=T. F. |last3=Mentel |first4=A. |last4=Kiendler-Scharr |first5=C. |last5=Spindler |first6=B. |last6=Bohn |first7=T. |last7=Brauers |first8=H. P. |last8=Dorn |first9=H. |last9=Fuchs |first10=R. |last10=Tillmann |first11=A. |last11=Wahner |first12=H. |last12=Saathoff |first13=K.-H. |last13=Naumann |first14=O. |last14=Mohler |first15=T. |last15=Leisner |first16=L. |last16=Muller |first17=M.-C. |last17=Reinnig |first18=T. |last18=Hoffmann |first19=K. |last19=Salo |first20=M. |last20=Hallquist |first21=M. |last21=Frosch |first22=M. |last22=Bilde |first23=T. |last23=Tritscher |first24=P. |last24=Barmet |first25=A. P. |last25=Praplan |first26=P. F. |last26=DeCarlo |first27=J. |last27=Dommen |first28=A. S. H. |last28=Prevot |first29=U. |last29=Baltensperger | year = 2012 | title = Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions | journal = Proceedings of the National Academy of Sciences | volume = 109| pages = 13503–13508| doi = 10.1073/pnas.1115186109 | issue = 34| pmid=22869714 | pmc=3427056|bibcode=2012PNAS..10913503D |doi-access=free }}</ref> Products of α-pinene which have been identified explicitly are [[pinonaldehyde]], [[norpinonaldehyde]], [[pinic acid]], [[pinonic acid]] and [[pinalic acid]].{{cn|date=February 2023}}

==Properties and usage==
α-Pinene is highly [[bioavailable]], with 60% human pulmonary uptake and rapid metabolism or redistribution.<ref name="russo2011"/> α-Pinene is an [[anti-inflammatory]] via [[PGE1]],<ref name="russo2011"/> and is likely [[antimicrobial]].<ref>{{cite journal | last1 = Nissen | first1 = L. | last2 = Zatta | first2 = A. | last3 = Stefanini | first3 = I. | last4 = Grandi | first4 = S. | last5 = Sgorbati | first5 = B. | last6 = Biavati | first6 = B. | year = 2010 | title = Characterization and [[antimicrobial]] activity of essential oils of industrial hemp varieties (''Cannabis sativa'' L.) | journal = Fitoterapia | volume = 81 | issue = 5| pages = 413–419 | doi=10.1016/j.fitote.2009.11.010| pmid = 19969046 |display-authors=etal}}</ref> It exhibits activity as an [[acetylcholinesterase inhibitor]], aiding memory.<ref name="russo2011"/> Like [[borneol]], [[verbenol]] and [[pinocarveol]] (−)-α-pinene is a [[allosteric modulator|positive modulator]] of [[GABAA receptor]]s. It acts at the [[benzodiazepine]] [[binding site]].<ref name="pmid27573669">{{cite journal |last1=Yang |first1=H. |last2=Woo |first2=J. |last3=Pae |first3=A.-N. |last4=Um |first4=M.-Y. |last5=Cho |first5=N.-C. |last6=Park |first6=K.-D. |last7=Yoon |first7=M. |last8=Kim |first8=J. |last9=Lee |first9=C.-J. |last10=Cho |first10=S. |title=α-Pinene, a major constituent of pine tree oils, enhances non-rapid eye movement sleep in mice through GABA<sub>A</sub>-benzodiazepine receptors |journal=Molecular Pharmacology |volume= 90|issue= 5|pages= 530–539|year=2016 |pmid=27573669 |doi=10.1124/mol.116.105080 |doi-access=free }}</ref>

α-Pinene forms the biosynthetic base for [[Cannabinoid receptor type 2|CB2]] ligands, such as [[HU-308]].<ref name="russo2011">{{cite journal |last=Russo |first=E. B. |title=Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects |journal=British Journal of Pharmacology |volume=163 |issue=7 |pages=1344–1364 |year=2011 |doi=10.1111/j.1476-5381.2011.01238.x |pmid=21749363 |pmc=3165946}}</ref>

α-Pinene is one of the many [[terpenes]] and [[terpenoids]] found in [[cannabis]] plants.<ref>{{cite journal|last1=Russo|first1=E. B.|last2=McPartland|first2=J. M.|date=2003|title=Cannabis is more than simply Δ<sup>9</sup>-tetrahydrocannabinol|journal=Psychopharmacology|volume=165|issue=4|pages=431–432|doi=10.1007/s00213-002-1348-z|pmid=12491031|s2cid=19504014}}</ref> These compounds are also present in significant levels in the finished, dried cannabis flower preparation commonly known as [[marijuana]].<ref>{{cite journal|last1=Turner|first1=C. E.|last2=Elsohly|first2=M. A.|last3=Boeren|first3=E. G.|date=1980|title=Constituents of ''Cannabis sativa'' L. XVII. A review of the natural constituents|journal=Journal of Natural Products|volume=43|issue=2|pages=169–234|doi=10.1021/np50008a001|pmid=6991645}}</ref> 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.<ref>{{cite journal|last1=Piomelli|first1=D.|last2=Russo|first2=E. B.|date=2016|title=The ''Cannabis sativa'' versus ''Cannabis indica'' debate: an interview with Ethan Russo, MD|journal=Cannabis and Cannabinoid Research|volume=1|issue=1|pages=44–46|doi=10.1089/can.2015.29003.ebr|pmid=28861479|pmc=5576603}}</ref> α-Pinene in particular is thought to reduce the memory deficits commonly reported as a side-effect of THC consumption.{{cn|date=November 2023}} It likely demonstrates this activity due to its action as an [[acetylcholinesterase inhibitor]], a class of compounds which are known to aid memory and increase alertness.<ref>{{cite journal|last1=Mahmoudvand|first1=H.|last2=Sheibani|first2=V.|last3=Keshavarz|first3=H.|last4=Shojaee|first4=S.|last5=Esmaeelpour|first5=K.|last6=Ziaali|first6=N.|date=2016|title=Acetylcholinesterase Inhibitor Improves Learning and Memory Impairment Induced by ''Toxoplasma gondii'' Infection|journal=Iranian Journal of Parasitology|volume=11|issue=2|pages=177–185|pmid=28096851|pmc=5236094}}</ref>{{Additional citation needed|date=November 2023|reason=This article is specific to Toxoplasma gondii infection, and does not make claims about alertness, only memory.}} 

α-Pinene also contributes significantly to many of the varied, distinct, and unique odor profiles of the multitude of marijuana strains, varieties and [[cultivars]].<ref>{{cite journal|last1=Mediavilla|first1=V.|last2=Steinemann|first2=S.|date=1997|title=Essential oil of ''Cannabis sativa'' L. strains.|journal=Journal of the International Hemp Association|volume=4|pages=80–82}}</ref>

== References ==
{{reflist|colwidth=32em}}

{{Acetylcholine metabolism and transport modulators}}
{{GABAA receptor positive modulators}}

{{DEFAULTSORT:Pinene, Alpha-}}
[[Category:Acetylcholinesterase inhibitors]]
[[Category:Antibiotics]]
[[Category:Bicyclic compounds]]
[[Category:Flavors]]
[[Category:Cycloalkenes]]
[[Category:GABAA receptor positive allosteric modulators]]
[[Category:Monoterpenes]]
[[Category:Cyclobutanes]]
[[Category:Plant communication]]
[[Category:Wood extracts]]