Equilibrium solubility, dissolution thermodynamics and preferential solvation of adenosine in aqueous solutions of N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethylsulfoxide and propylene glycol

Abstract

The equilibrium solubility of adenosine in co-solvent mixtures of {(N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethylsulfoxide and propylene glycol)+water} were determined experimentally by the isothermal dissolution equilibrium method in the temperature range of (278.15–323.15) K under atmospheric pressure of 101.0kPa. The maximum solubility was observed in neat N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethylsulfoxide or propylene glycol. The mole fraction solubility of adenosine increased with increasing temperature and mass fraction of co-solvent in each binary system. At the same temperature and mass fraction of the organic solvent, the solubility of adenosine was greater in (N-methyl-2-pyrrolidone+water) than in the other three mixed solvents. The Jouyban-Acree model, Van’t Hoff-Jouyban-Acree model and Apelblat-Jouyban-Acree model were employed to correlate the measured solubility data. The largest values of relative average deviation and root-mean-square deviation were 4.87×10−2 and 3.52×10−4, respectively. Positive values of the dissolution enthalpy illustrated that the dissolution process of adenosine in these mixed solvents was endothermic. Moreover, the preferential solvation parameters were derived from their thermodynamic solution properties by using the inverse Kirkwood–Buff integrals. For the four co-solvent mixtures with intermediate composition and co-solvent-rich mixtures, adenosine is preferentially solvated neither by organic solvent nor by water. However, adenosine is preferentially solvated by water in water-rich mixtures. Adenosine could act mainly as a Lewis base interacting with acidic hydrogen atoms of water.