Solvent effects on the thermodynamic functions of dissociation of anilines and phenols

For a systematic series of phenols and some a n i l i n e s , the thermodynamic functions of proton dissociation have been determined i n a 50 weight per cent water-methanol solvent system. The technique used was the e.m.f.-spectrophotometric method» The results obtained have been compared against those obtained for the same compounds in water solvent alone. For phenols, the change i n free energy on t r a n s f e r r i n g from water to the mixed solvent system has been found to arise from a change i n entropy - and therefore to a change in solvation - assuming entropy e f f e c t s are p r i m a r i l y due to solvation e f f e c t s. In the case of a n i l i n e s , solvation e f f e c t s are minor, because of no anion s o l v a t i o n , both i n water and mixed solvent systems.