Pinene

Pinene is a collection of unsaturated bicyclic monoterpenes. Two geometric isomers 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 conifers.^[3] Pinenes are also found in many non-coniferous plants such as camphorweed (Heterotheca)^[4] and big sagebrush (Artemisia tridentata).

Pinene

Pinene
Names
IUPAC names (1S,5S)-2,6,6-trimethylbicyclo[3.1.1]hept-2-ene (1S,5S)-6,6-dimethyl-2-methylenebicyclo[3.1.1]heptane
Identifiers
CAS Number	(mixture): 1330-16-1 Y (1R-α): 7785-70-8 Y (1S-α): 7785-26-4 Y (1R-β): 19902-08-0 Y (1S-β): 18172-67-3 Y
3D model (JSmol)	(mixture): Interactive image
ChEBI	(mixture): CHEBI:17187 (1R-α): CHEBI:28261 (1S-α): CHEBI:28660 (1S-β): CHEBI:50025
ChemSpider	(1R-α): 74205 (1S-α): 389795 (1R-β): 8466294 (1S-β): 14198
ECHA InfoCard	100.029.170
EC Number	(1R-α): 232-087-8
PubChem CID	(1R-α): 82227 (1S-α): 15837102 (1R-β): 10290825 (1S-β): 440967
UNII	(mixture): 996299PUKB Y (1R-α): H6CM4TWH1W Y (1S-α): TZR3GM95PR Y (1R-β): IGO73S04D5 Y (1S-β): AFN153A7SU Y
CompTox Dashboard (EPA)	(mixture): DTXSID7041671
SMILES (mixture): CC1=CCC2CC1C2(C)C
Properties
Chemical formula	C10H16
Molar mass	136.24 g/mol
Appearance	Liquid
Density	0.86 g·cm−3 (alpha, 15 °C)[1][2]
Melting point	−62 to −55 °C (−80 to −67 °F; 211 to 218 K) (alpha)[1]
Boiling point	155 to 156 °C (311 to 313 °F; 428 to 429 K) (alpha)[1]
Solubility in water	Practically insoluble in water
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Isomers

skeletal formula
perspective view	X		X
ball-and-stick model			X
name	(1R)-(+)-α-pinene	(1S)-(−)-α-pinene	(1R)-(+)-β-pinene	(1S)-(−)-β-pinene
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 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.^[5]

Biosynthesis of pinene from geranyl pyrophosphate

Plants

Alpha-pinene is the most widely encountered terpenoid in nature^[6] and is highly repellent to insects.^[7]

Alpha-pinene appears in conifers and numerous other plants.^[8] Pinene is a major component of the essential oils of Sideritis spp. (ironwort)^[9] and Salvia spp. (sage).^[10] Cannabis also contains alpha-pinene^[8] and beta-pinene.^[11] Resin from Pistacia terebinthus (commonly known as terebinth or turpentine tree) is rich in pinene. Pine nuts produced by pine trees contain pinene.^[8]

Makrut lime fruit peel contains an essential oil comparable to lime fruit peel oil; its main components are limonene and β-pinene.^[12]

The racemic mixture of the two forms of pinene is found in some oils like eucalyptus oil.^[13]

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.^[14][15]

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 pinanehydroperoxide. The hydroboration of α-pinene has been extensively examined. With borane-dimethylsulfide, two equivalents of α-pinene react to give (diisopinocampheyl)borane.^[16] Reaction with 9-BBN gives the reagent called alpine borane. This sterically crowded chiral trialkylborane can stereoselectively reduce aldehydes in what is known as the Midland Alpine borane reduction.^[17]

β-Pinene

β-Pinene can be converted to α-pinene in the presence of strong bases,^[18] or pyrolysed to produce myrcene at 400 °C.

Use

Pinenes, especially α, are the primary constituents of turpentine, a nature-derived solvent and fuel.^[3]

The use of pinene as a biofuel in spark ignition engines has been explored.^[19] Pinene dimers have been shown to have heating values comparable to the jet fuel JP-10.^[5]