α-Pinene is an organic compound of the terpene class, one of the two isomers of pinene. It is an alkene and contains a reactive four-membered ring. It is found in the oils of many coniferous species, particularly pine. It is also found in the essential oil of rosemary (Rosmarinus officinalis)3 or Cannabis.4 Both enantiomers are known in nature; the (1S,5S)- or (-)-α-pinene is more common in European pines, while the (1R,5R)- or (+)-α-isomer is more common in North America. North. The racemic mixture is present in some oils, such as eucalyptus oil and orange peel oil.