Terpinolene is a monocyclic monoterpene hydrocarbon widely found in plant essential oils, especially in certain cannabis chemotypes, tea tree, lilac, pine, and conifer-type oils. It contributes to a complex, fresh aroma blending citrus, floral, piney, and sometimes herbal sensations and has attracted increasing interest for its antioxidant, antimicrobial, anticancer-related, and insecticidal activities.
Chemical Structure and Basic Properties
Terpinolene has the molecular formula C₁₀H₁₆ and an average molecular mass of 136.23 g·mol⁻¹. It is an isomeric form of the terpinene group and is classified as a p-menthadiene, with a six-membered cyclohexene ring, a double bond within the ring (at C1–C2), and a second, isopropenyl-type double bond at C4(8). This conjugated diene system contributes to its volatility, reactivity, and characteristic scent.
Physical and Solubility Characteristics
Physically, terpinolene is a colorless to light yellow, mobile, volatile liquid with a boiling point around 186 °C, a density of about 0.86 g·cm⁻³, and a refractive index near 1.4900. It is highly hydrophobic (experimental water solubility around 0.0095 mg·mL⁻¹ at 23 °C) and lipophilic (experimental logP ≈ 4.47), with very low miscibility in water but high solubility in ethanol, diethyl ether, and other common organic solvents.
