5-Nitrosalicylaldehyde in aqueous co-solvent mixtures of methanol, ethanol, isopropanol and acetonitrile: Solubility determination, solvent effect and preferential solvation analysis

Abstract

The equilibrium 5-nitrosalicylaldehyde solubility in methanol (1) + water (2), ethanol (1) + water (2), isopropanol (1) + water (2) and acetonitrile (1) + water (2) mixtures was determined by a shake-flask method from 273.15 K to 313.15 K under local pressure of 101.2 kPa. At the same mass fraction of methanol (ethanol, isopropanol or acetonitrile) and temperature, the mole fraction solubility of 5-nitrosalicylaldehyde was greater in (acetonitrile + water) mixture than in ethanol (1) + water (2), isopropanol (1) + water (2) and methanol (1) + water (2) mixtures. The relative importance of solute–solvent and solvent–solvent interactions upon the solubility variation was valued by using the linear solvation energy relationship analysis of solvent effect. The method of inverse Kirkwood–Buff integrals was used to study the preferential solvation on the basis of thermodynamic solution properties. The preferential solvation parameters for methanol, ethanol, isopropanol and acetonitrile were positive in the four mixtures in co-solvent-rich and intermediate composition, indicating that 5-nitrosalicylaldehyde was solvated preferentially by the co-solvent. It is conjecturable that in these regions 5-nitrosalicylaldehyde acts as a Lewis acid with the alcohols’ molecules; while for the acetonitrile + water mixture, the preferential solvation could be attributed to polarization effects. Moreover, the drugs’ solubility was mathematically represented via the Jouyban-Acree model acquiring the average relative deviations<6.03%.