Longifolene is a naturally occurring tricyclic sesquiterpene hydrocarbon extracted from pine oleoresins, valued for its characteristic woody aroma and its importance in fragrance synthesis as well as in organic chemistry applications.
Chemical Structure and Properties
Longifolene (C₁₅H₂₄, MW 204.35) exhibits a distinctive tricyclic framework with four methyl groups and an exocyclic methylene group. The naturally occurring enantiomer shows a positive optical rotation (+42.73°). It is typically observed as a pale yellow, viscous oil with a pine-like odor, low solubility in water, and a boiling point of approximately 274°C.
Its rigid molecular structure confers significant stability and resistance to common sesquiterpene rearrangements, making it particularly suitable for selective chemical functionalization in synthetic processes.
Natural Sources and Extraction
Longifolene is predominantly found in Pinus roxburghii (chir pine) turpentine, where it can represent between 20% and 78% of the heavy fraction. It is commonly isolated through fractional distillation of crude turpentine under reduced pressure conditions.
Additional minor sources include lapsang souchong tea, where it originates from pinewood smoking processes, as well as certain liverwort species.
