Interactions between Ethyl Lactate and Substituted Ethanols or Ethyl Acetate: Thermodynamic, FT-IR Spectroscopic, DFT Method, and PC-SAFT EoS Studies

Abstract

In the present study, measurements of the experimental density (ρ), speed of sound (c), and refractive index (n_D) of binary liquid mixtures of ethyl lactate (EL) with 2-aminoethanol (2-AE), 2-chloroethanol (2-CE), and ethyl acetate (EA) have been carried out within the temperature range from 298.15 to 323.15 K with an interval of 5 K and at 0.1 MPa. Excess volume (V^E), isentropic compressibility (k_s), excess isentropic compressibility (k_s^E), and excess refractive index (n_D^E) for the above liquid mixtures were calculated from the experimental measurements and they were correlated with the Redlich–Kister equation. Also, we obtained good fitting results in the computation of the density with perturbed chain statistical associating fluid theory equation of state and predictive results in the computation of the refractive index and speed of sound with several mixing rules and Nomoto’s relation, respectively. Further, we measured the Fourier-transform infrared (FT-IR) spectral data of pure liquids and their mixtures at different concentrations and simulated the molecular interactions using density functional theory (DFT) calculations for the 3 sets of binary systems with the ADF 2020.102 package at the GGA BP86-D3 level of theory with TZP. Apart from these, the type and nature of molecular interactions and structural effects were studied between the component molecules with the aid of excess thermodynamic properties, FT-IR measurements, and DFT calculations.