Solubility and Dissolution Behavior Analysis of 7‑Azaindole in Pure and Binary Mixture Solvents at Temperatures Ranging from 278.15 to 323.15 K

in this paper, the solubility of 7-azaindole was measured in nine pure solvents (ethanol, isopropanol, n-propanol, methanol, EA, acetone, acetonitrile, n-hexane, tetrahydrofuran, THF) as well as in three binary mixed solvents (acetone + n-hexane, THF + n-hexane, and isopropanol + n-hexane) by a gravimetric method at temperatures from 278.15 to 323.15 K under atmospheric pressure. The solubility of 7-azaindole in selected solvents is closely related to the temperature and solvent composition: in nine pure solvents, the order of solubility of 7-zazindole is THF > acetone > methanol > isopropanol ≥ EA > ethanol > acetonitrile > n-hexane when the temperature is below 298.15 K. Nevertheless, as the temperature increases continually (298.15–328.15 K), the order of solubility changes to THF > acetone > methanol > isopropanol > n-propanol > ethanol > EA > acetonitrile > n-hexane; in three binary mixed solvents, both the temperature and solvent composition can influence the solubility of 7-azaindole, and the latter has a greater impact. The modified Apelblat model, λh model, Jouyban–Acree model, and CNIBS/R–K equation were used to correlate the experimental value. In these models, the Apelblat equation is more suitable for correlating 7-azaindole solubility in nine pure solvents; however, for three binary mixed solvents, the solubility of 7-azaindole is closer to the simulated value of the Jouyban–Acree model. Moreover, the KAT LASER model was used to deeply understand the influence of solvents on the solubility of 7-azaindole by multiple linear regression analysis (MLRA) of the solvent parameters involved in this model.