Differential Hydration of Phenol and Phenoxy Radical and the Energetics of the Phenol O−H Bond in Solution

Abstract

Monte Carlo simulations and thermodynamic perturbation theory calculations have been carried out to analyze the differential hydration of phenol (PhOH) and phenoxy radical (PhO•). The hydration enthalpy of phenol predicted by different phenol−water interaction models is in good agreement with experimental data. On the basis of the difference in the hydration enthalpy of phenol and phenoxy radical, we find that the O−H bond dissociation enthalpy in water is above the recommended experimental value for the gas phase by ca. 7 kcal/mol. This result is in agreement with photoacoustic calorimetry measurements for phenol in other polar solvents. Thermodynamic perturbation theory results for the relative hydration Gibbs energy of phenol and phenoxy radical are also reported. The structure of the solutions suggests that the differential solvation of phenol and phenoxy radical can be related to the strong character of phenol as a hydrogen bond donor in comparison with the role played by phenoxy radical as a hydroge...