Thermodynamics Research Center / ThermoML | Thermochimica Acta

ABSTRACT

Relative permittivities, r O , and refractive indices, D n , have been measured at (293.15- 303.15) K, for the mixtures 1-pentanol + 2,5,8,11,14-pentaoxapentadecane (TEGDME) or TEGDME + octane. These data have been used, together with density measurements available in the literature, to calculate the correlation factors, K g , according to the Kirkwood-Frohlich equations. The ' O r curves of the 1-pentanol + TEGDME system are shifted to high mole fractions of the alcohol, and show a rather large minimum. The shape of the curves of methanol + TEGDME or + polyethylene glycol dimethyl ether 250 (PEG-250) mixtures is similar. This reveals that polyethers can break the alcohol self-association even at high alkanol concentrations. The higher r ' O values of the methanol solutions are ascribed to large selfassociation of this type alcohol. The r ' O curves of the 1-pentanol + dibutyl ether (DBE) system are nearly symmetrical, and the r ' O values are higher than those of the corresponding TEGDME mixture. This indicates that effects related to the alcohol self-association are much relevant in the DBE system. These findings are supported by K g and molar polarization data. Values of molar refraction of 1-pentanol systems reveal that dispersion forces become more important in the sequence: octane less than DBE less than TEGDME. Such forces are also more relevant in the 1-pentanol + TEGDME system than in the methanol + TEGDME solution. The comparison of r O and K g data for TEGDME or DBE + octane mixtures shows than the polyether is a more structured liquid.