Ternary Phase Equilibrium of Adenine + Hydrogen Peroxide + Water and Characterization of the Adduct of Adenine with Hydrogen Peroxide

In this study, the solid–liquid phase equilibrium of the ternary adenine (C5H5N5) + hydrogen peroxide (H2O2) + water (H2O) system at 283.15 and 293.15 K under atmospheric pressure (p = 101.1 kPa) was determined using the isothermal saturation methodology. The solubility data of adenine in various concentrations of hydrogen peroxide solutions were determined, and two ternary phase diagrams were built using the wet residue method of Schreinemakers. At a certain temperature, two pure solids corresponding to pure adenine and pure C5H5N5·H2O2 adduct appeared in each equilibrium system. As the temperature dropped, the saturated areas of pure C5H5N5·H2O2 adduct and adenine increased. Under the same conditions, the saturated region of the C5H5N5·H2O2 adduct was significantly larger than that of adenine. In addition, the C5H5N5·H2O2 adduct produced based on the ternary phase diagram of C5H5N5 + H2O2 + H2O was characterized by infrared spectra, X-ray powder diffraction, thermogravimetry, and morphology. In addition, the influence of ethanol upon the solid–liquid phase equilibrium was investigated. Addition of ethanol increases the solubility of adenine and C5H5N5·H2O2 adduct.