Intermolecular interactions in formamide + 2-alkoxyethanols: Viscometric study

The viscosity (η) of formamide (FA) with 2-methoxyethanol (2-ME) and 2-ethoxyethanol (2-EE) has been measured at 303.15, 308.15, 313.15, 318.15 and 323.15 K over the entire composition range. From the experimental viscosity data, viscosity deviations (Δη) of binary mixtures were evaluated and fitted to the Redlich–Kister equation. The Δη values are positive over the entire range of composition for (formamide + 2-methoxyethanol) and (formamide + 2-ethoxyethanol) systems. The Grunberg–Nissan (d12), Tamura–Kurata (T12) and Hind (H12) interaction parameters have been calculated. Furthermore, Gibbs free energy of activation (ΔG*), enthalpy of activation (ΔH*), entropy of activation (ΔS*) and excess Gibbs free energy of activation (ΔG*E) of viscous flow have also been evaluated by using Eyring viscosity equation. The results are discussed in terms of molecular interactions due to physical, chemical and structural effects between the unlike molecules. It is observed that the strength of intermolecular interaction between FA and 2-alkoxyethanol molecules is in order: FA + 2-EE > FA + 2-ME.