Solubility, solution thermodynamics and preferential solvation for 4-bromopyrazole in mixed solvents of (methanol/ethanol + water) from T = (283.15 to 318.15) K

Abstract

The solubility of 4-bromopyrazole in binary (methanol+water) and (ethanol+water) solvent mixtures were investigated by using the isothermal dissolution equilibrium method under atmosphere pressure. The maximum solubility was observed in neat methanol or ethanol. At the same mass fraction of methanol or ethanol and temperature, the solubility of 4-bromopyrazole was greater in (ethanol+water) than in (methanol+water) mixed solvents. The obtained solubility data were correlated with Jouyban-Acree model, modified Apelblat-Jouyban-Acree model and van’t Hoff-Jouyban-Acree model. The largest values of relative average deviation and the root-mean-square deviation were 3.59×10−2 and 6.60×10−3, respectively. Positive apparent enthalpies showed that dissolution of 4-bromopyrazole in these mixed solvents was an endothermic process. Preferential solvation parameters of 4-bromopyrazole were also derived by means of the inverse Kirkwood-Buff integrals method. The preferential solvation parameter was negative in water-rich mixtures but positive in intermediate composition and alcohol-rich mixtures. In the latter case, it is conjecturable that 4-bromopyrazole is acting as a Lewis acid with alcohol molecules. The co-solvent action may be related to the breaking of the ordered structure of water around the polar moieties of 4-bromopyrazole which increases the solvation of this solute. The solubility data and thermodynamic study expanded the physicochemical information about 4-bromopyrazole in binary solvent mixtures.