This paper reports the densities, refraction indices, and vapor liquid equilibria for binary systems ester + n-triethyl-2-hydroxyethylammonium hexanoate (m-2-HEAH): methyl acetate (1) + m-2-HEAH (2), ethyl acetate (1) + m-2-HEAH, and propyl acetate (1) + m-2-HEAH (2). The excess molar volumes, deviations in the refraction index, apparent molar volume, and thermal expansion coefficient for the binary systems were fitted to polynomial equations; The, Peng-Robinson equation of state, coupled with the Wong-Sandler mixing rule, is used to describe the experimental data Since the predictive activity coefficient model COSMO-SAC is used in the Wong-Sandler mixing rule, the resulting thermodynamic model is a completely predictive one. The prediction results for the density and for the vapor liquid equilibria have a deviation lower than 1.6% and 1.1%, respectively.