Rimsulfuron solubility in several aqueous solutions revisited: Solvent effect, dissolution behavior and preferential solvation

Abstract

Preferential solvation was analyzed with the help of the inverse Kirkwood–Buff integrals method based on the available equilibrium solubility of rimsulfuron in four solutions of EG (1) + water (2), ethanol (1) + water (2), DMF (1) + water (2) and methanol (1) + water (2). Rimsulfuron was preferentially surrounded by water solvent in water-rich composition regions. For the aqueous ethanol/methanol mixtures in intermediate and methanol/ethanol-rich composition ranges, methanol/ethanol preferentially solvated rimsulfuron; while EG/DMF didn’t preferentially solvate the rimsulfuron for the EG/DMF in the ranges. Selective solvation of rimsulfuron by methanol/ethanol was perhaps resulted from higher basicity of methanol/ethanol that was in favor of interactions with the acidic groups of rimsulfuron. The performance of rimsulfuron solubility was investigated by means of Hansen solubility parameter concept in detail. The study on relative prominence of solvent–solvent and solute–solvent molecule interactions on rimsulfuron solubility variation identified the hydrogen-bond basicity, dipolarity-polarizability and solubility parameter of solution descriptors analyzed in terms of the linear solvation energy relationships. As well, the dissolution and transfer Gibbs free energy change, enthalpy and entropy were resulted, representing the solubilization capacity more favorable with the rising compositions of EG/ethanol/DMF/methanol. Thermodynamic analysis of enthalpy–entropy compensation demonstrated a shift of dominant dissolution mechanism from entropy-driven (water-rich regions) to enthalpy-driven (organics-rich regions).