Thermophysical Properties and Molecular Interactions in Binary Mixtures of Oxolane with 2-Alkoxyethanols

Densities (ρ), viscosities (η), and refractive indices (n_D) have been measured for binary mixtures of oxolane (tetrahydrofuran, THF) with 2-alkoxyethanols (2-ethoxyethanol, EE; 2-butoxyethanol, BE) over the entire composition range and at temperatures from 298.15 to 323.15 K in 5 K increments. From these data, excess molar volume (V_m^E), thermal expansivity (α), excess thermal expansivity (α^E), deviation in viscosity (Δη), free energy for the activation of viscous flow (ΔG^≠) and its excess (ΔG^≠E), and deviation in refractive index (Δn_D) were calculated. The variations in these properties with the composition and temperature indicate that cross-hydrogen bonding, chain length effects, and molecular packing play significant roles in both EE + THF and BE + THF systems. The measured ρ, η, and n_D data were fitted to concentration-dependent polynomial equations, while excess properties (V_m^E, Δη, ΔG^≠E, and Δn_D) were fitted to Redlich–Kister-type equations. Densities were additionally correlated using the Jouyban-Acree model. The correlating abilities of various viscosity models (McAllister three-body, McAllister four-body, and Ausländer) were also evaluated. Furthermore, density functional theory, a quantum mechanical approach, was used to assess intra- and intermolecular interactions within the binary mixtures.