Molecular Interactions Between Ethyl Lactate and Higher Alkanols: Thermodynamics, Spectroscopic, DFT, and QTAIM Studies

Thermodynamic and structural effects of a binary system with ethyl lactate (EL) and higher 1‐alkanols were studied using experimental and computational approaches. Hence, density ( ρ ), speed of sound ( c ), and refractive index ( n D ) for (EL + 1‐heptanol, 1‐octanol, and 1‐nonanol) binary systems were measured at different temperatures and at 0.1 MPa. From these experimental data, thermodynamic properties: excess volume ( V E ), isentropic compressibility ( k s ), excess isentropic compressibility , and excess refractive index were calculated. Further, the Redlich–Kister polynomial equation was used to fit the excess properties, and the resulting analysis focused on examining structural effects and interactions at the molecular level. Knowledge of these molecular interactions will allow us to develop more effective separation strategies, improve process efficiency, and reduce energy consumption of industrial separation units. Moreover, FT‐IR spectra were obtained for both pure components and their mixtures at various mole fractions, and density functional theory (DFT) calculations were carried out for three sets of binary systems using the ADF 2020.102 package to discern the type of interactions that are prevailing between liquid molecules. The excess volume and excess isentropic compressibility were positive, whereas the excess refractive index was negative for all the binary systems.