l-Limonene is the optical isomer of Limonene. It is classified as three types: l-Limonene, d-Limonene optical isomers and one racemic.
It is a colorless to pale yellow liquid with strong fruity and citrus odor.
d-Limonene is naturally found in Pine needle oil, Turpentine, Cajeput oil and other essential oils. l-Limonene presents in essential oil of citrus, such as mandarin oil and sweet orange oil.
Racemic limonene is derived from turpentine. It mainly used in food flavour and synthetic fragrances.
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. Beta-Phellandrene is widely distributed in essential oils (Angelica, Eucalyptus, Lavandula, Mentha, Pinus species).
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. Consequently, beta-Phellandrene is widely used in flavor industry.