Solute–solvent interactions in the (N,N-dimethylformamide + N-methylformamide + water) ternary system at 298.15 K

Abstract

This work reports on a variety of experiments carried out as a contribution to the understanding of the structure and dynamics of amide–water mixtures. The densities and viscosities of the ternary mixture N,N-dimethylformamide (DMF) + N-methylformamide (NMF) + water (W) and the binary mixture (DMF + NMF) were measured over the whole composition range at 298.15 K and atmospheric pressure. The densities and viscosities measured compare fairly well with those calculated using several empirical methods available for predicting properties of ternary mixtures starting from the data of the binary ones. From these measurements, values for excess molar volumes, mixing viscosities and molar excess Gibbs energies for the activation of viscous flow were calculated and fitted to the equations proposed by Redlich–Kister for binary mixtures and Cibulka for ternary mixtures. The values of these functions reveal that binary associations are prevalent in the water-rich region of the ternary mixture and, to a lower degree, ternary associates in the DMF-rich region. Several predictive models were used to calculate the viscosity of the ternary mixture.