Thermochemical properties of sesquiterpenes in natural products by correlation gas chromatography: Application to bergamotene oil

The vapor pressures and vaporization enthalpies of the three major components of bergamotene oil have been evaluated by correlation gas chromatography. Three major components were identified by GCMS as E β-caryophyllene, trans α-bergamotene and α-humulene. Two of the components, E β-caryophyllene and α-humulene were also evaluated using commercial caryophyllene samples. Z-caryophyllene, present in the commercial sample was also evaluated. Two sets of hydrocarbon standards, n-alkanes and a series of relatively unrelated cyclic compounds that included adamantane and two alkyl derivatives, (−) α-pinene, diamantane and 1,4-di-t-butylbenzene, were used. Vaporization enthalpies of the targets at T = 298.15 K were reproduced within the specified uncertainties by both sets of standards as were vapor pressures from T = (298.15 to ∼400)K. Above 400 K, vapor pressures diverged. Equations for the evaluation of vapor pressure as a function of temperature are reported for all four compounds investigated.