Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

Limiting activity coefficients (?18) of six branched pentanols (2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, and 3-methyl-2-butanol) in water were measured at several temperatures covering the range from the melting to the normal boiling point of water. Five experimental techniques, namely, inert gas stripping, headspace analysis in two variants, the classical and the relative, Rayleigh distillation, and the method of circulation still, were employed for the purpose. A comprehensive review is further presented of experimental data on the limiting activity coefficients, ?18, infinite dilution partial molar excess enthalpies (1E,8), and heat capacities (p,1E,8) of these aqueous solutes. Since 1E,8 data for 2-methyl-1-butanol in water are lacking in the literature, they were also determined in this work. For each pentanol isomer, the compiled data were critically evaluated and together with the data measured in this work correlated with a suitable model equation providing adequate simultaneous description of the equilibrium measurements and the calorimetric information. As a result, a recommended thermodynamically consistent temperature dependence of ?18, 1E,8, and p,1E,8 of superior accuracy was established in the range from the melting point to the normal boiling point of water. In addition, by employing literature data on the respective residual properties of pure pentanols, analogous recommendations were derived also for the temperature dependence of the Henry s law constants, hydration enthalpies, and hydration heat capacities. Variation of these various infinite dilution thermodynamic properties with temperature and pentanol branching is briefly discussed. Furthermore, the performance of five predictive approaches to estimate ?18(T) of aqueous pentanols was tested.