Vapor pressure and vaporization enthalpy studies of (+)-longifolene, (−)-isolongifolene and β-myrcene by correlation gas chromatography

This paper examines the use of two different sets of standards, n-alkanes and a more structurally diverse group of cyclic and polycyclic molecules to evaluate the vaporization enthalpies and vapor pressures of (+) longifolene(−)-isolongifolene and β-myrcene using correlation gas chromatography. Both sets of standards provide similar vaporization enthalpies and vapor pressures of the title compounds at  T = 298.15 K within their experimental uncertainties. The group of cyclic and polycyclic hydrocarbons reproduce the vapor pressures of the sesquiterpene hydrocarbons at elevated temperatures best while the same properties of β-myrcene are best reproduced by the n-alkanes as judged by reproduction of both experimental boiling temperatures measured at reduced pressures and vapor pressures. The results confirm previous findings obtained on polycyclic hydrocarbons regarding the suitability of using structurally similar standards and suggest that n-alkanes are suitable vapor pressure standards for highly unsaturated acyclic hydrocarbons.