Densities, viscosities, and excess properties for binary mixtures of ethylene glycol with amides at 308.15 K

Abstract

The densities, ρ, and viscosities, η, of binary mixtures of ethylene glycol with formamide, N,N-dimethyl formamide and N,N-dimethyl acetamide, have been measured over the entire composition range at 308.15 K. From this experimental data, excess molar volume, $V_{\text{m}}^{\text{E}}$, deviation in viscosity, Δη, and excess Gibbs free energy of activation of viscous flow, $\Delta G^{{ * {\text{E}}}},$ have been determined. Negative values of $V_{\text{m}}^{\text{E}}$, Δη, and $\Delta G^{{ * {\text{E}}}}$ are observed over the entire composition range in the mixtures studied. The observed negative values of various excess and deviation parameters are attributed to the existence of strong interactions, like dipole–dipole interactions, H-bonding between the carbonyl group of amide molecules, and hydroxyl group of glycol molecules, geometrical fitting of smaller molecules into the voids created by larger molecules in the liquid mixtures. The excess properties have been fitted to Redlich–Kister-type polynomial, and the corresponding standard deviations have been calculated. The derived partial molar volumes and excess partial molar volumes also support the $V_{\text{m}}^{\text{E}}$ results. The experimental viscosity data of all of these liquid mixtures have been correlated with four viscosity models.