Thermodynamics of mixing tetrahydrofuran with 1-alkanols and excess enthalpies of homomorphy-related systems

Densities, rho, and volumetric heat capacities, C-p/V, have been measured at 298.15 K over the whole mole fraction range for the binary mixtures {tetrahydrofuran + methanol, + ethanol, + 1-propanol, + 1-butanol, + 1-hexanol, + 1-heptanol, + 1-octanol, + 1-nonanol, or + 1-decanol}. From experimental data, the excess molar isobaric heat capacities, C-p(E), were calculated. Excess molar volumes, V-E, are reported for the systems containing methanol and 1-decanol. The apolar homomorph concept has been used in semiquantitative calculations intended to assess and to compare the degrees of heteroassociation in these mixtures by getting an approximation to the corresponding negative enthalpic contributions at equimolar fraction, H-int. With this aim, excess molar enthalpies, H-E, of {tetrahydrofuran + nonane} and {cyclopentane + 1-butanol, + 1-pentanol, + 1-hexanol, + 1-heptanol, + 1-octanol, + 1-nonanol, or + 1-decanol} have been measured at 298.15 K. The results are discussed in terms of molecular interactions. Particularly, the various steps of W-shape concentration dependence found in the CpE point to the occurrence of local nonrandomness in {THF + alkanol} mixtures.