Thermochemistry of dissolution of aniline in mixtures of water with methanol and tert-butyl alcohol

The enthalpies of dissolution (Delta H(sol)degrees) of aniline in mixtures of water with methanol and tert-butyl alcohol were determined in the whole concentration range of mixed solvents at 25 degrees C. Maxims of endothermi city were found in both systems at similar to 0.3 and similar to 0.06 molar fractions, respectively. The data obtained were compared with the thermoch emical characteristics of the nonelectrolytes studied previously (dimethyls ulfoxide, nitromethane, formamide, etc.). The conclusion was drawn that the behavior of aniline in water-alcohol mixtures is mainly determined by its proton-donating ability and solvation of the benzene ring. A comparison of acoustic data and spectral and thermodynamic characteristics showed that th ermochemical data are the most sensitive indicator for energy and structura l changes occurring upon variation of the composition of a mixed solvent.