Vapor Pressures and Vaporization, Sublimation, and Fusion Enthalpies of Some Fatty Acids

Sublimation enthalpies are calculated at T/K = 298.15 by combining both literature and measured vaporization enthalpies with available fusion enthalpies of a series of saturated and unsaturated fatty acids. The results are used to predict vapor pressures of both the subcooled liquid and solid state for those materials that are solids at T/K = 298.15. Equations for the prediction of vapor pressure from T/K = 298.15 to the boiling temperature are provided for all liquid materials studied. The results are compared to vapor pressures in the literature measured by other methods. Vaporization enthalpies were measured for the following compounds by correlation gas chromatography (ΔH_vap(298.15 K), kJ·mol^–1): α-linolenic acid, (136.9 ± 10.4); γ-linolenic acid, (135.9 ± 6.8); linoleic acid, (134.1 ± 10.3); elaidic acid, (133.0 ± 10.3); heneicosanoic acid, (149.2 ± 7.1); erucic acid, (149.2 ± 7.1); and docosanoic acid (154.7 ± 7.3). A solid–solid transition enthalpy and fusion enthalpy, respectively, for docosanoic acid by differential scanning calorimetry (DSC) was also measured (kJ·mol^–1, K): (3.57 ± 0.3, 340.9 ± 0.2); (66.3 ± 0.2, 352.3 ± 0.1). The saturated acids that were studied include tetradecanoic acid through to docosanoic acid.