Solubility, modelling, preferential solvation and solvent effect of 2-amino-6-chloropyrazine in ten pure mono-solvents and four solvent mixtures at 278.15 K to 323.15 K

Abstract

Equilibrium solubility of 2-amino-6-chloropyrazine in ten pure solvents (methanol, ethanol, n-propanol, isopropanol, N,N-Dimethylformamide (DMF), acetonitrile, acetone, propylene glycol (PG), ethylene glycol (EG) and water) and four binary blends of ethanol/n-propanol/PG/DMF plus water was experimentally measured by isothermal saturation method at 278.15 K to 323.15 K under p = 101.2 kPa. The maximum mole fraction of 2-amino-6-chloropyrazine in mono-solvents was obtained in neat acetone (5.053 × 10-2) at 323.15 K. For four binary mixed systems, the amount of 2-amino-6-chloropyrazine dissolved in DMF + water was more than other three systems. For pure solvent systems, the temperature was the only factor that affected the dissolution of 2-amino-6-chloropyrazine, while temperature and solvent composition were both the factors that affected the dissolution of 2-amino-6-chloropyrazine. The solubility data of 2-amino-6-chloropyrazine in pure solvents was correlated with apelblat model, van’t Hoff model and Buchowski–Książczak λh model. The Jouyban-Acree model, Apelblat-Jouyban-Acree model and van’t Hoff-Jouyban-Acree model were applied to calculate the solubility data of 2-amino-6-chloropyrazine in mixtures. The van’t Hoff plots of the solubility of 2-amino-6-chloropyrazine was adopted as a method to show the relationship between ln × and 1/T-1/Thm, which was the basis for calculating thermodynamic properties. The preferential solvation performance in mixed systems was estimated by the values of δx1,3, in 0.19 < xn-propanol/PG/DMF < 1 and 0.23 < xethanol < 1, the 2-amino-6-chloropyrazine was preferentially dissolved in organic solvents. In contrast, the 2-amino-6-chloropyrazine was dissolved preferentially in water in other intervals. What’s more, the solvent effect of 2-amino-6-chloropyrazine in mixed systems was obtained, the hydrogen bond interaction was the only factor that affects dissolution in alcohols + water and the solvent–solvent molecular interaction was dominant in DMF + water.