Thermodynamics of mixtures containing alkoxyethanols - Part XV. DISQUAC characterization of systems of alkoxyethanols with n-alkanes or cyclohexane

Binary mixtures of alkoxyethanols, CH3-(CH2)n-O-(CH2CH2O)(m)OH and n-alkane s or cyclohexane are characterized in terms of DISQUAC. The corresponding d ispersive (DIS) and quasichemical (QUAC) interchange coefficients, C(eh, l) (DIS/QUAC)f or the (e,h) contacts (type e, -O-; type h, -OH) are given. In comparison with the values for 1-alkanol + monooxalkane systems, the proxim ity effects in CH3-(CH2)(n)-O-CH2-CH2-OH + n-alkane mixtures lead to an inc rease in the C(eh, l)(DIS)and C-eh,C-l (QUAC) coefficients and to a decreas e in Ce-h,2(DIS). For other hydroxyethers (3-methoxypropanol, 4-methoxybuta nol), the C-eh, l(QUAC)(l =1,2) coefficients approach those of 1-alkanol monooxalkane mixtures with increasing separation between the -O- and -OH- g roups. However, the C-eh, 2(DIS) coefficient is still lower than in alcohol ic solutions, indicating that proximity effects in the framework of DISQUAC remain. DISQUAC yields a consistent description of the vapor-liquid equili bria, VLE, and of liquid-liquid equilibria, LLE. Good results are obtained for azeotropic data. The coordinates of the critical points are represented over a reasonable range of composition and temperature. Excess molar entha lpies H-m(E) and the excess molar heat capacity at constant pressure, C-pm( E), are well reproduced. The typical large deviations for properties at inf inite dilution, excess molar partial enthalpies, H(m)(E,infinity)and natura l logarithms of activity coefficients, ln y(i)(infinity), of the associated compound are found. Thermodynamic properties of alkoxyethanol + alkane mix tures are determined by the self-association of the polar compound via both inter- and intramolecular H-bonds, as well as by dipole-dipole interaction s between alkoxyethanol molecules. These interactions are analyzed in terms of the effective dipole moments (<(<mu>)over bar>) and are more important than in 1-alkanol + alkane mixtures. The dipole-dipole interactions in syst ems with alkoxyethanols decrease along a homologous series, and are enhance d by the presence of two ether atoms. Intramolecular H-bonds are more relev ant than the intermolecular H-bonds and become weakened with the separation between the -O- and -OH groups of the hydroxyethers.