Phellandrene

Phellandrenes
α-Phellandrene α-Phellandrene	β-Phellandrene β-Phellandrene
Names
	IUPAC names (α): 2-Methyl-5-(propan-2-yl)cyclohexa-1,3-diene; (β): 3-Methylidene-6-(propan-2-yl)cyclohex-1-ene
Identifiers
CAS Number	(α): 99-83-2 ; (β): 555-10-2 ; (−)-(α): 4221-98-1 ; (+)-(α): 2243-33-6 ;
3D model (JSmol)	(α): Interactive image; (β): Interactive image; (−)-(α): Interactive image; (+)-(α): Interactive image;
ChEBI	(β): CHEBI:48741; (−)-(α): CHEBI:301; (+)-(α): CHEBI:367; (−)-(β): CHEBI:129; (+)-(β): CHEBI:53;
ChemSpider	(α): 7180 ; (β): 10669 ;
ECHA InfoCard	100.014.121
EC Number	(α): 202-792-5; (β): 209-081-9; (−)-(α): 224-167-6;
KEGG	(−)-(α): C09875; (+)-(α): C11391; (−)-(β): C11392; (+)-(β): C09877;
PubChem CID	(α): 7460; (β): 11142; (−)-(α): 442482; (+)-(α): 443160; (−)-(β): 443161;
UNII	(α): 49JV13XE39 ; (β): 2KK225M001 ; (−)-(α): 56UV8X65K0 ; (+)-(α): E45FS72C5K ;
CompTox Dashboard (EPA)	(α): DTXSID8051673 ;
	InChI (α): InChI=1S/C10H16/c1-8(2)10-6-4-9(3)5-7-10/h4-6,8,10H,7H2,1-3H3 Key: OGLDWXZKYODSOB-UHFFFAOYSA-N; (β): InChI=1S/C10H16/c1-8(2)10-6-4-9(3)5-7-10/h4,6,8,10H,3,5,7H2,1-2H3 Key: LFJQCDVYDGGFCH-UHFFFAOYSA-N; (−)-(α): InChI=1S/C10H16/c1-8(2)10-6-4-9(3)5-7-10/h4-6,8,10H,7H2,1-3H3/t10-/m1/s1 Key: OGLDWXZKYODSOB-SNVBAGLBSA-N; (+)-(α): InChI=1S/C10H16/c1-8(2)10-6-4-9(3)5-7-10/h4-6,8,10H,7H2,1-3H3/t10-/m0/s1 Key: OGLDWXZKYODSOB-JTQLQIEISA-N;
	SMILES (α): CC1=CCC(C=C1)C(C)C; (β): CC(C)C1CCC(=C)C=C1; (−)-(α): CC1=CC[C@@H](C=C1)C(C)C; (+)-(α): CC1=CC[C@H](C=C1)C(C)C;
Properties
Chemical formula	C10H16
Molar mass	136.24 g/mol
Appearance	Colorless oil (α and β)
Density	α: 0.846 g/cm3; β: 0.85 g/cm3
Boiling point	α: 171-172 °C; β: 171-172 °C
Solubility in water	Insoluble (α and β)
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H226, H304
Precautionary statements	P210, P233, P240, P241, P242, P243, P280, P301+P310, P303+P361+P353, P331, P370+P378, P403+P235, P405, P501
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Phellandrenes are organic compounds with the formula C₁₀H₂₀. have a similar molecular structure and similar chemical properties. α-Phellandrene and β-phellandrene are cyclic monoterpenes and are double-bond isomers. In α-phellandrene, both double bonds are endocyclic, and in β-phellandrene, one of them is exocyclic. Both are insoluble in water, but miscible with organic solvents.

Etymology and occurrence

α-Phellandrene was named after Eucalyptus phellandra, now called Eucalyptus radiata, from which it can be isolated.^[2] It is also a constituent of the essential oil of Eucalyptus dives.^[3] β-Phellandrene has been isolated from the oil of water fennel and Canada balsam oil. The main source of β-phellandrene is terpentine.^[4]

β-pinene is a source of β-phellandrene.^[4]

Reactions and uses

α-Phellandrene undergoes hydrochlorination to give phellandrene hydrochloride (a cyclohexenyl chloride). Base hydrolysis of this hydrochloride gives piperitol.^[4]

The phellandrenes are used in fragrances because of their pleasing aromas. The odor of β-phellandrene has been described as peppery-minty and slightly citrusy.

Like other cyclohexadienes, α-phellandrene reacts with ruthenium trichloride to give (cymene)ruthenium chloride dimer.

Biosynthesis

The biosynthesis of phellandrene begins with dimethylallyl pyrophosphate and isopentenyl pyrophosphate condensing in an S_N1 reaction to form geranyl pyrophosphate. The resultant monoterpene undergoes cyclization to form a menthyl cationic species. A hydride shift then forms an allylic carbocation. Finally, an elimination reaction occurs at one of two positions, yielding either α-phellandrene or β-phellandrene.^[5]

Safety

The α-phellandrene isomer can form hazardous and explosive peroxides on contact with air at elevated temperatures.^[6]

References

^ The Merck Index, 12th Edition, 7340, 7341
^ Jacobs, S.W.L., Pickard, J., Plants of New South Wales, 1981, ISBN 0-7240-1978-2.
^ Boland, D. J., Brophy, J. J., and A. P. N. House, Eucalyptus Leaf Oils, 1991, ISBN 0-909605-69-6.
^ ^a ^b ^c Sell, Charles S. (2006). "Terpenoids". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.2005181602120504.a01.pub2. ISBN 0471238961.
^ Dewick, Paul M. (9 March 2009). Medicinal natural products : a biosynthetic approach (3rd ed.). Chichester, West Sussex, United Kingdom. ISBN 9780470741689. OCLC 259265604.{{cite book}}: CS1 maint: location missing publisher (link)
^ Urben, Peter (2007). Bretherick's Handobook of Reactive Chemical Hazards. Vol. 1 (7 ed.). Butterworth-Heinemann. p. 1154.