dl-isoprenaline hydrochloride solubility in four binary solvents at saturation: Thermodynamic analysis, Hansen solubility parameters and molecular simulation

The solubility properties of dl-isoprenaline hydrochloride (dl-IPN) in four kinds of binary-solvents systems {( n -propanol, n -butanol, 2-propoxyethanol and 2-butoxyethanol) + methanol} at temperature range of 278.15–323.15 K under 101.3 kPa was further investigated using the laser monitoring technique. According to the result about solubility of dl-IPN in these chosen binary solvents, it is obvious that dl-IPN is more soluble at higher temperature. Additionally, the solubility values of dl-IPN, in all the investigated binary solvent mixtures, is improved with increasing mass fraction of co-solvent (methanol). The Hansen solubility parameters (HSPs) interpretate reasonably the order of dl-IPN solubility in these binary-solvents systems. Furthermore, the molecular dynamic (MD) simulation is employed to describe the molecular interactions of the types solute–solvent and solvent–solvent, and the obtained results confirm that solute–solvent and solvent–solvent molecular interactions have deep impact on the solubility of dl-IPN. The obtained experimental data about the solubility of dl-IPN is fitted by five models ( λh equation, Apelblat equation, Jouyban-Acree-Apelblat (J-A-A) model, Ma model and Sun model). The analysis of thermodynamic properties was based on the values of the calculated thermodynamic parameters. It can be concluded that the dl-IPN dissolution process is entropy-motivated and endothermal in all the investigated binary-solvents systems, and that the main contribution to Δ dis G o is due to enthalpy.