Thermophysical study of the binary mixtures of triethyl phosphate with N-methylformamide, N,N-dimethylformamide and N,N-dimethylacetamide – Experimental and theoretical approach

Abstract

Abstract Densities at (293.15, 298.15, 303.15 and 308.15) K, and viscosities and ultrasonic velocities at 298.15 K of binary liquid mixtures of triethyl phosphate with N-methylformamide, N,N-dimethylformamide and N,N-dimethylacetamide have been measured over the entire range of composition at p = 0.1 MPa. From the experimental data, values of excess molar volume, excess isentropic compressibility, viscosity deviation and excess Gibbs energy of activation for viscous flow have been calculated. These results were fitted to the Redlich-Kister-type polynomial equation. The viscosity deviations and the excess Gibbs energy were found to be positive for the all systems investigated, while the excess volumes and the excess isentropic compressibilities were negative for TEP + DMA and for TEP + DMF systems, and positive for mixtures TEP + NMF. These results were interpreted based on the strength of the specific interaction, size and shape of molecules. Molecular dynamics simulations were used to provide a detailed explanation of the differences between the TEP + NMF and other systems, which were ultimately traced to strong hydrogen bonding between NMF and TEP.