Physicochemical and spectroscopic study of molecular interactions in N-methylformamide + ethylene/diethylene/triethylene glycol binary systems at temperatures from 293.15 to 323.15 K: Experimental and theoretical approach

This work examines the molecular interactions in NMF + glycol mixtures by evaluating their thermophysical properties and FTIR spectral data. For this purpose, the measurements of the densities, ρ and speeds of sound, u of NMF + ethylene glycol (EG), + diethylene glycol (DEG) and + triethylene glycol (TEG) binary mixtures were carried out across the entire range of mole fraction at temperatures, T/K= (293.15–323.15) and pressure, p = 100 kPa. The experimental ρ and u data were correlated using the Jouyban-Acree model to examine their composition and temperature dependence. The excess properties, viz., excess molar volume, excess isentropic compressibility, excess intermolecular free length, excess speed of sound, excess molar isentropic compressibility and excess acoustic impedance were evaluated from the measured data. Further, the partial molar volume/compressibility; excess partial molar volume/compressibility of the components across entire composition range and at infinite dilution were also calculated. The trends in these parameters have been interpreted in footings of molecular interactions in these systems. Also, the speeds of sound were evaluated theoretically by means of various theories/relations and the results were compared with experimental data. Additionally, the FT-IR spectra of pure NMF, EG and near equimolar NMF + EG mixture were recorded and examined to validate the nature of dominant intermolecular interactions. Furthermore, Density functional theory (DFT) and theoretical IR spectral calculations were performed to confirm the intermolecular CO⋅⋅⋅⋅⋅H–O hydrogen-bonding interactions in these NMF + glycol binary systems.