Electron Density Dependent Composition of the Solvation Shell of Phenol Derivatives in Binary Solutions of Water and Ethanol

The dynamic motions of solvent molecules in the solvation shell of phenols in binary water-ethanol solutions have been examined experimentally by measuring the solvent relaxation times using phase-fluorometry. The results show that the mono-exponential character of the solvent relaxation changes to bi-exponential just after the ethanol content of the bulk solution exceeds a critical value. This value depends on the electron density of the aromatic rings of the phenolic molecules. Above the critical values much higher ethanol content is observed in the solvation shell compared to the bulk solutions. This observation is applicable in wide scale of chemical processes in condensed phase and indicates that further research is needed towards development of a picture at the atomic scale.