Phellandrene is the name for a pair of organic compound

Organic compound

An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

s that have a similar molecular structure and similar chemical properties. α-Phellandrene and β-phellandrene are cyclic monoterpenes

Terpene

Terpenes are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are often strong smelling and thus may have had a protective...

 and are double-bond isomer

Isomer

In chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...

s. 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

Diethyl ether

Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...

.

α-Phellandrene was named after Eucalyptus phellandra, now called Eucalyptus radiata

Eucalyptus radiata

Eucalyptus radiata is a medium to tall tree to 30 m high with persistent bark on the trunk and larger branches or persistent to smaller branches. The bark shortly fibrous , grey to grey-brown, shedding in long ribbons...

, from which it can be isolated. It is also a constituent of the essential oil

Essential oil

An essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants. Essential oils are also known as volatile oils, ethereal oils or aetherolea, or simply as the "oil of" the plant from which they were extracted, such as oil of clove...

 of Eucalyptus dives

Eucalyptus dives

Eucalyptus dives or broad-leaved peppermint is a small tree native to temperate dry sclerophyll woodlands and forests of south-eastern Australia. The juvenile leaves are ovate and glaucus, and adult leaves are lanceolate to broad-lanceolate. Leaves are aromatic.-Uses:There are two notable...

. β-Phellandrene has been isolated from the oil of water fennel

Fennel

Fennel is a plant species in the genus Foeniculum . It is a member of the family Apiaceae . It is a hardy, perennial, umbelliferous herb, with yellow flowers and feathery leaves...

 and Canada balsam

Canada balsam

Canada balsam, also called Canada turpentine or balsam of fir, is a turpentine which is made from the resin of the balsam fir tree of boreal North America...

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 alpha phellandrene isomer can form hazardous and explosive peroxides on contact with air at elevated temperature.