Title: a-Phellandrene
CAS Registry Number: 99-83-2
CAS Name: 2-Methyl-5-(1-methylethyl)-1,3-cyclohexadiene
Additional Names: p-mentha-1,5-diene; 5-isopropyl-2-methyl-1,3-cyclohexadiene; 4-isopropyl-1-methyl-1,5-cyclohexadiene
Molecular Formula: C10H16
Molecular Weight: 136.23
Percent Composition: C 88.16%, H 11.84%
Literature References: Isoln of l-form from essential oils of Eucalyptus dives Schau. and E. phellandra Baker & Smith, Myrtaceae: Smith et al., J. Chem. Soc. 123, 1657 (1923). Isoln of d-form from oil of bitter fennel (Foeniculum vulgare Mill., Umbelliferae): Wallach, Ann. 336, 9 (1904). Structure: Semmler, Ber. 36, 1749 (1903). Synthesis of dl-form: Read, Storey, J. Chem. Soc. 1930, 2770; B. Singaram, J. Verghese, Indian J. Chem. 14B, 1003 (1976). Configuration: Burgstahler et al., J. Am. Chem. Soc. 83, 4660 (1961). Circular dichroism: G. Snatzke et al., Tetrahedron Lett. 1966, 4551. Review: J. L. Simonsen, The Terpenes vol. 1 (Univ. Press, Cambridge, 2nd ed., 1947) pp 193-204; B. Singaram, J. Verghese, Perfum. Flavor. 2, 33-38 (1978).
Derivative Type: l-Form
CAS Registry Number: 4221-98-1
Properties: Mobile oil. bp758 171-172°; bp16 58-59°. d420 0.8410. nD20 1.4709. [a]D20 -217°. Practically insol in water; sol in ether.
Boiling point: bp758 171-172°; bp16 58-59°
Optical Rotation: [a]D20 -217°
Index of refraction: nD20 1.4709
Density: d420 0.8410
Derivative Type: d-Form
CAS Registry Number: 2243-33-6
Properties: Mobile oil. bp16 66-68°. d425 0.8463. nD25 1.4777. [a]D16 +86.4°. Practically insol in water; sol in ether.
Boiling point: bp16 66-68°
Optical Rotation: [a]D16 +86.4°
Index of refraction: nD25 1.4777
Density: d425 0.8463
CAUTION: Can be irritating to, and absorbed through, skin. Ingestion can cause vomiting, diarrhea.
Use: In fragrances.
alpha-Phenylacetamide alpha-Phenylbutyramide alpha-Phenylcinnamic Acid alpha-Phenylglycine alpha-Picoline

CAS number 99-83-2 YesY, (α)
555-10-2 (β)
Jmol-3D images Image 1
Molecular 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)
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Phellandrene is the name for a pair of organic compounds that 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 ether.

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

The α-phellandrene isomer can form hazardous and explosive peroxides on contact with air at elevated temperature.[4]