Proton transfer in mixed water-organic solvent solutions: Correlation between rate, equilibrium constant, and the proton free energy of transfer

We demonstrate that the proton dissociation reaction of excited 1-aminopyrene follows a simple structure-reactivity correlation in water-methanol, water-DMSO, water-dioxane, and water-acetonitrile binary mixtures. The role of the proton free energy of transfer from pure water to the binary mixtures, ΔG_t^w,s(H⁺) in determining the rate of transfer is also demonstrated. We have extended our analysis to include neutral ROH type photoacids where the simultaneous creation of the anion during proton transfer affects the energetics of the dissociation reaction in the mixed solvents as compared to pure water.