Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

Relative permittivities, er , at 1 MHz have been measured for (1-alkanol + cyclohexylamine) systems at T = (293.15 to 303.15) K and atmospheric pressure. The excess permittivity values, eEr , Kirkwood s correlation factors, gK, and the excess values of this magnitude, gE K, have been also determined for these solutions and, using measurements available in the literature, for mixtures containing a number of 1-alkanols and n-propylamine, n-butylamine, aniline, N-methylaniline, pyridine, di-n-ethylamine, N,N-dimethylformamide, N,N-dimethylacetamide, di-n-propylether, di-n-butylether, 2,5,8,11,14-pentaox apentadecane, or propanal. At /1 (volume fraction) = 0.5, eErvalues of cyclohexylamine solutions change in the sequence: 1-propanol greater than 1-butanol greater than 1-heptanol less than 1-decanol and the symmetry of the eEr curves becomes skewed to higher /1 values when the alcohol size increases. This seems to be a rather general behavior as is also encountered for many of the systems investigated. It can be explained in terms of the weaker and lower self-association of longer 1-alkanols. The analysis of gK data shows that cyclohexylamine solutions including shorter alcohols are more structured. In addition, mixtures with this cyclic amine are more structured than those containing a linear amine or aniline. The eEr o/1P and gE K o/1P curves of (1-alkanol + amine) mixtures show similar patterns. Thus, negative eEr values can be ascribed to the real mixture is less structured than the ideal solution; positive eEr values are due to the system is more structured than the ideal solution. We have also determined the orientational polarization and the corresponding excess values, PE m. The PE m and gE K functions have the same sign That is, negative values of such magnitudes suggest that the loss of structure of the real mixture compared with that of the ideal solution can be ascribed, at least in part, to a weakening of the orientational polarization.