Solubility modelling and dissolution properties of 5-phenyltetrazole in thirteen mono-solvents and liquid mixtures of (methanol + ethyl acetate) at elevated temperatures

Abstract

The solid-liquid phase equilibrium of 5-phenyltetrazole in thirteen mono-solvents including methanol, ethanol, n-propanol, isopropanol, acetone, 2-butanone, acetonitrile, ethyl acetate, toluene, 1,4-dioxane, cyclohexane, dimethyl sulfoxide (DMSO), N,N-dimethyl formamide (DMF) and liquid mixtures (methanol+ethyl acetate) were obtained experimentally via the isothermal saturation method within the temperatures from (283.15 to 318.15)K under about 101.2kPa. It was intuitive to notice that the solubility values of 5-phenyltetrazole in studied solvents increased with increasing temperature. The descending order of the solubility data in different mono-solvents was as follows: DMSO>DMF>acetone>methanol>(ethanol, 2-butanone)>isopropanol>n-propanol>1,4-dioxane>ethyl acetate>acetonitrile>toluene>cyclohexane. For the binary solvent mixtures of (methanol+ethyl acetate) with given initial compositions, the maximum solubility was observed in neat methanol. The solubility data in mono-solvents were correlated and calculated by using the modified Apelblat equation and the Buchowski-Książczak λh equation; and in the binary solvent mixtures, by three cosolvency models. The largest values of RAD and RMSD were 1.25% and 4.83×10−4, respectively. The apparent dissolution enthalpy was positive, illustrating that the dissolution process of 5-phenyltetrazole was endothermic. Finally, the preferential solvation parameters (δx1,3) of 5-phenyltetrazole in (methanol+ethyl acetate) mixtures at (293.15–313.15)K were derived by using the inverse Kirkwood–Buff integrals method. The δx1,3 values were positive in methanol-rich compositions and negative in the other regions.