Solid-liquid equilibrium of 2,3-dimethoxybenzoic acid in fifteen mono-solvents: Determination, Correlation, Hansen solubility parameter, molecular dynamic simulation and thermodynamic analysis

Abstract

This current research work was devoted to investigating solid–liquid equilibrium solubility, Hansen solubility parameters (HSPs), intermolecular interaction and thermodynamic analysis of 2,3-dimethoxybenzoic acid (o-veratric acid) in fifteen mono-solvent systems namely “water, methanol (MtOH), ethanol (EtOH), n-propanol (NPOH), isopropanol (IPOH), n-butanol (NBOH), methyl acetate (MtAC), ethyl acetate (EtAC), n-propyl acetate (NPAC), isopropyl acetate (IPAC), n-butyl acetate (NBAC), ethylene glycol monomethyl ether (EGME), ethylene glycol monoethyl ether (EGEE), 1,4-dioxane (Diox) and acetonitrile (MeCN)” by experimentation, mathematical relationships and molecular simulations. The measurement of solubility of o-veratric acid was conducted by laser monitoring method under 0.1 MPa, and corresponding measuring temperature range was 278.15 K to 323.15 K in most mono-solvents except Diox (288.15 K ∼ 323.15 K). The maximum of o-veratric acid solubility expressed in mole faction was found in Diox at 323.15 K (0.1717), while the minimum of solubility value was observed as 4.791e-3 in water at 278.15 K. At 298.15 K, o-veratric acid solubility in selected solvents had a general order of: Diox ≈ EGME > EGEE > MtOH > MtAC > EtOH > EtAC > MeCN > NPOH > NPAC > IPOH > NBOH > IPAC ≈ NBAC > water. Molecular similarities between o-veratric acid and fifteen selected mono-solvents were deeply considered with the help of HSPs concept. Moreover, solubility values were computationally expressed by Margules, Wilson, NRTL, NRTL-SAC and UNIQUAC model with the average relative deviation (ARD) of no higher than 5.365%. For explaining solubility behavior of o-veratric acid, molecular electrostatic potential surface, Hirschfeld surface as well as solvation free energy of o-veratric acid were analyzed by molecular simulation. Furthermore, the dissolution thermodynamic properties (ΔdisG, ΔdisH and ΔdisS) of o-veratric acid dissolving in selected solvents and mixing thermodynamic properties (ΔmixG, ΔmixH and ΔmixS) of o-veratric acid with fifteen solvents were estimated by UNIQUAC model, the results of which indicated the dissolution processes were spontaneous, endothermic as well as entropy increasing and mixing processes were spontaneous as well as entropy-increasing.