View source for Pinene

{{Short description|Oily organic chemical found in plants}}
{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 446720672
| Name = Pinene
| ImageFile = Alpha-pinen.svg
| ImageSize = 150px
| ImageName = Pinene
| IUPACName = (1''S'',5''S'')-2,6,6-trimethylbicyclo[3.1.1]hept-2-ene <br/> (1''S'',5''S'')-6,6-dimethyl-2-methylenebicyclo[3.1.1]heptane
| OtherNames =
|Section1={{Chembox Identifiers
| SMILES = CC1=CCC2CC1C2(C)C
| index_label = (mixture)
| index2_label = (1''R''-α)
| index3_label = (1''S''-α)
| index4_label = (1''R''-β)
| index5_label = (1''S''-β)
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 1330-16-1
| CASNo2_Ref = {{cascite|correct|CAS}}
| CASNo2 = 7785-70-8
| CASNo3_Ref = {{cascite|correct|CAS}}
| CASNo3 = 7785-26-4
| CASNo4_Ref = {{cascite|correct|CAS}}
| CASNo4 = 19902-08-0
| CASNo5_Ref = {{cascite|correct|CAS}}
| CASNo5 = 18172-67-3
| ChEBI = 17187
| ChEBI2 = 28261
| ChEBI3 = 28660
| ChEBI5 = 50025
| ChemSpiderID2 = 74205
| ChemSpiderID3 = 389795
| ChemSpiderID4 = 8466294
| ChemSpiderID5 = 14198
| EC_number2 = 232-087-8
| PubChem2 = 82227
| PubChem3 = 15837102
| PubChem4 = 10290825
| PubChem5 = 440967
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 996299PUKB
| UNII2_Ref = {{fdacite|correct|FDA}}
| UNII2 = H6CM4TWH1W
| UNII3_Ref = {{fdacite|correct|FDA}}
| UNII3 = TZR3GM95PR
| UNII4_Ref = {{fdacite|correct|FDA}}
| UNII4 = IGO73S04D5
| UNII5_Ref = {{fdacite|correct|FDA}}
| UNII5 = AFN153A7SU
| RTECS =
  }}
|Section2={{Chembox Properties
| Formula = C<sub>10</sub>H<sub>16</sub>
| MolarMass = 136.24 g/mol
| Appearance = Liquid
| Density = 0.86 g·cm<sup>−3</sup> (alpha, 15 °C)<ref name="GESTIS">{{GESTIS|ZVG=491170|CAS=80-56-8|Name=alpha-Pinen|Date=07-January-2016}}</ref><ref name="GESTIS beta">{{GESTIS|ZVG=492888|Name=beta-Pinen|Date=07-January-2016}}</ref>
| Solubility = Practically insoluble in water
| MeltingPtC = −62 to −55
| MeltingPt_notes = (alpha)<ref name="GESTIS"/>
| BoilingPtC = 155 to 156
| BoilingPt_notes = (alpha)<ref name="GESTIS"/>
  }}
}}
'''Pinene''' is a collection of unsaturated bicyclic [[monoterpene]]s. Two geometric [[isomer]]s of pinene are found in nature, [[α-pinene]] and [[β-pinene]]. Both are chiral. As the name suggests, pinenes are found in [[pines]].  Specifically, pinene is the major component of the liquid extracts of [[Pinophyta|conifers]].<ref name=terp>{{Ullmann |doi=10.1002/14356007.a27_267|title=Turpentines |year=2000 |last1=Gscheidmeier |first1=Manfred |last2=Fleig |first2=Helmut |isbn=3527306730 }}</ref> Pinenes are also found in many non-coniferous [[plant]]s such as camphorweed (''[[Heterotheca]]'')<ref>{{Cite journal|vauthors=Lincoln DE, Lawrence BM|date=1984|title=The Volatile Constituents of Camphorweed, ''Heterotheca subaxillaris''|journal=Phytochemistry|volume=23|issue=4|pages=933–934|doi=10.1016/S0031-9422(00)85073-6|bibcode=1984PChem..23..933L }}</ref> and big sagebrush (''[[Artemisia tridentata]]'').

== Isomers ==
{| class="wikitable" style="margin:1em auto; text-align:center;"
| '''[[skeletal formula]]'''||[[Image:(1R)-(+)-alpha-pinene-2D-skeletal.png|100px]]||[[Image:(1S)-(-)-alpha-pinene-2D-skeletal.png|100px]]||[[Image:(1R)-(+)-beta-pinene-2D-skeletal.png|100px]]||[[Image:(1S)-(-)-beta-pinene-2D-skeletal.png|100px]]
|-
| '''perspective view'''||X||[[Image:(1S)-(-)-alpha-pinene-2D-projected-skeletal.png|120px]]||X||[[Image:(1S)-(-)-beta-pinene-2D-projected-skeletal.png|120px]]
|-
| '''[[ball-and-stick model]]'''||[[Image:(−)-alpha-pinene-3D-balls.png|120px]]||[[Image:(1S)-(−)-alpha-pinene-from-xtal-3D-balls.png|120px]]||X||[[Image:(1S)-(−)-beta-pinene-from-xtal-3D-balls.png|120px]]
|-
| '''name'''||(1''R'')-(+)-α-pinene||(1''S'')-(−)-α-pinene||(1''R'')-(+)-β-pinene||(1''S'')-(−)-β-pinene
|-
| '''[[CAS registry number|CAS number]]'''||7785-70-8||7785-26-4||19902-08-0||18172-67-3
|}

== Biosynthesis ==
α-Pinene and β-pinene are both produced from [[geranyl pyrophosphate]], via cyclisation of [[linalool|linaloyl]] pyrophosphate followed by loss of a proton from the carbocation equivalent. Researchers at the Georgia Institute of Technology and the Joint BioEnergy Institute have been able to synthetically produce pinene with a bacterium.<ref name=":0">{{Cite journal|vauthors=Sarria S, Wong B, Martín HG, Keasling JD, Peralta-Yahya P|date=2014|title=Microbial Synthesis of Pinene|journal=ACS Synthetic Biology|volume=3|issue=7|pages=466–475|doi=10.1021/sb4001382|pmid=24679043|doi-access=free}}{{open access}}</ref>

[[Image:Pinene_biosynthesis_en.svg|600px|center|Biosynthesis of pinene from geranyl pyrophosphate]]

==Plants==
[[Alpha-pinene]] is the most widely encountered terpenoid in nature<ref name="noma2010">{{Cite book|url=https://www.taylorfrancis.com/books/e/9780429155666|title=Handbook of Essential Oils: Science, Technology, and Applications|vauthors=Noma Y, Asakawa Y|publisher=CRC Press|year=2010|isbn=9780429155666|veditors=Baser KH, Buchbauer G|edition=2nd|location=Boca Raton, FL|pages=585–736|chapter=Biotransformation of Monoterpenoids by Microorganisms, Insects, and Mammals|doi=10.1201/b19393 }}</ref> and is highly repellent to insects.<ref name="nerio2010">{{cite journal |vauthors=Nerio LS, Olivero-Verbel J, Stashenko E |title=Repellent activity of essential oils: a review |journal=Bioresour Technol |volume=101 |issue=1 |pages=372–378 |year=2010 |doi=10.1016/j.biortech.2009.07.048 |pmid=19729299|bibcode=2010BiTec.101..372N }}</ref>

Alpha-pinene appears in [[conifers]] and numerous other plants.<ref name="russo2011"/> Pinene is a major component of the essential oils of ''[[Sideritis]]'' spp. (ironwort)<ref>{{Cite journal|vauthors=Köse EO, Deniz İG, Sarıkürkçü C, Aktaş Ö, Yavuz M|date=2010|title=Chemical composition, antimicrobial and antioxidant activities of the essential oils of Sideritis erythrantha Boiss. and Heldr. (var. erythrantha and var. cedretorum P.H. Davis) endemic in Turkey|journal=Food and Chemical Toxicology|volume=48|issue=10|pages=2960–2965|doi=10.1016/j.fct.2010.07.033|pmid=20670669}}</ref> and
''[[Salvia]]'' spp. (sage).<ref>{{Cite journal|display-authors=6|vauthors=Özek G, Demirci F, Özek T, Tabanca N, Wedge DE, Khan SI, Başer KH, Duran A, Hamzaoglu E|date=2010|title=Gas chromatographic-mass spectrometric analysis of volatiles obtained by four different techniques from Salvia rosifolia Sm., and evaluation for biological activity|journal=Journal of Chromatography A|volume=1217|issue=5|pages=741–748|doi=10.1016/j.chroma.2009.11.086|pmid=20015509}}</ref> ''[[Cannabis]]'' also contains alpha-pinene<ref name="russo2011">{{cite journal|vauthors=Russo EB|date=2011|title=Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects|journal=British Journal of Pharmacology|volume=163|issue=7|pages=1344–1364|doi=10.1111/j.1476-5381.2011.01238.x|pmc=3165946|pmid=21749363}}</ref> and [[Beta-Pinene|beta-pinene]].<ref>{{Cite journal|vauthors=Hillig KW|date=2004|title=A chemotaxonomic analysis of terpenoid variation in Cannabis|journal=Biochemical Systematics and Ecology|volume=32|issue=10|pages=875–891|doi=10.1016/j.bse.2004.04.004|bibcode=2004BioSE..32..875H }}</ref> Resin from ''[[Pistacia terebinthus]]'' (commonly known as terebinth or turpentine tree) is rich in pinene. [[Pine nuts]] produced by [[Pinaceae|pine]] trees contain pinene.<ref name="russo2011"/>

[[Kaffir lime|Makrut lime]] fruit peel contains an essential oil comparable to lime fruit peel oil; its main components are limonene and β-pinene.<ref name="kasuan">{{cite journal|vauthors=Kasuan N|date=2013|title=Extraction of ''Citrus hystrix'' D.C. (Kaffir Lime) Essential Oil Using Automated Steam Distillation Process: Analysis of Volatile Compounds|url=http://www.ukm.my/mjas/v17_n3/Nurhani.pdf|journal=Malaysian Journal of Analytical Sciences|volume=17|issue=3|pages=359–369}}</ref>

The racemic mixture of the two forms of pinene is found in some oils like eucalyptus oil.<ref>{{Cite web|title=alpha-Pinene - Compound Summary|url=https://pubchem.ncbi.nlm.nih.gov/compound/alpha-pinene#section=Top|access-date=14 Nov 2017|website=PubChem|publisher=[[National Center for Biotechnology Information|NCBI]]}}</ref>

== Reactions ==
===α-Pinene===
Selective oxidation of α-pinene occurs at the allylic position to give [[verbenone]], along with pinene oxide, as well as verbenol and its hydroperoxide.<ref>{{cite journal|vauthors=Neuenschwander U, Guignard F, Hermans I|date=2010|title=Mechanism of the Aerobic Oxidation of α-Pinene|journal=ChemSusChem|language=de|volume=3|issue=1|pages=75–84|doi=10.1002/cssc.200900228|pmid=20017184|doi-access=free|bibcode=2010ChSCh...3...75N }}</ref><ref>{{cite journal |doi=10.15227/orgsyn.072.0057|title=(1R,5R)-(+)-Verbenone of High Optical Purity |journal=Organic Syntheses |year=1995 |volume=72 |page=57|author=Mark R. Sivik, Kenetha J. Stanton, Leo A. Paquette }}</ref>

[[Image:Verbenone by oxidation of pinene.png|center|250px|Pinene left verbenone right]]

α-Pinene can be converted to [[camphor]] by way of [[isobornyl acetate]].
[[Hydrogenation]] of pinene gives [[pinane]], precursor to a useful pinane[[hydroperoxide]].  
The [[hydroboration]] of α-pinene has been extensively examined. With [[borane-dimethylsulfide]], two equivalents of α-pinene react to give (diisopinocampheyl)borane.<ref>{{cite journal |doi=10.15227/orgsyn.092.0026|title=Preparation of Crystalline (Diisopinocampheyl)borane |year=2015 |last1=Abbott |first1=Jason |first2=Christophe|last2=Allais|first3=William R.|last3=Roush|
journal=Organic Syntheses |volume=92 |pages=26–37 |doi-access=free }}</ref> Reaction with [[9-Borabicyclo(3.3.1)nonane|9-BBN]] gives the reagent called [[alpine borane]]. This sterically crowded [[Chirality (chemistry)|chiral]] trialkylborane can [[stereoselective]]ly reduce aldehydes in what is known as the [[Midland Alpine borane reduction]].<ref>{{cite journal |last1=Midland |first1=M. Mark |title=B -3-Pinanyl-9-borabicyclo[3.3.1]nonane |journal=Encyclopedia of Reagents for Organic Synthesis |date=15 April 2001 |doi=10.1002/047084289X.rp173|isbn=0-471-93623-5 }}</ref>

===β-Pinene===
β-Pinene can be converted to α-pinene in the presence of strong bases,<ref>{{cite journal |doi=10.15227/orgsyn.065.0224|title=(a)-b-PINENE BY ISOMERIZATION OF (B)-b-PINENE |journal=Organic Syntheses |year=1987 |volume=65 |page=224|author=Charles A. Brown, Prabhakav K. Jadhav }}</ref> or pyrolysed to produce [[myrcene]] at 400&nbsp;°C.

==Use==
Pinenes, especially α, are the primary constituents of [[turpentine]], a nature-derived solvent and fuel.<ref name=terp/>

The use of pinene as a biofuel in [[Spark-ignition engine|spark ignition engines]] has been explored.<ref>{{Cite journal|vauthors=Raman V, Sivasankaralingam V, Dibble R, Sarathy SM|date=2016|title=α-Pinene - A High Energy Density Biofuel for SI Engine Applications|journal=SAE Technical Paper|series=SAE Technical Paper Series|volume=1|doi=10.4271/2016-01-2171}}</ref> Pinene [[Dimer (chemistry)|dimers]] have been shown to have heating values comparable to the [[JP-10 (fuel)|jet fuel JP-10]].<ref name=":0" />

== References ==
{{reflist}}

== Bibliography ==
* {{cite book|first1=J.|last1=Mann|first2=R. S.|last2=Davidson|first3=J. B.|last3=Hobbs|first4=D. V.|last4=Banthorpe|first5=J. B.|last5=Harborne|title=Natural Products|pages=[https://archive.org/details/isbn_9780582060098/page/309 309–311]|publisher=Addison Wesley Longman Ltd.|location=Harlow, UK|year=1994|isbn=978-0-582-06009-8|url-access=registration|url=https://archive.org/details/isbn_9780582060098/page/309}}

[[Category:Monoterpenes]]
[[Category:Cyclobutanes]]
[[Category:Cyclohexenes]]
[[Category:Wood extracts]]