Proton exchange in solutions of water in nitromethane and dioxane

The rates of proton exchange in the reaction H2O + D2O reversible arrow 2HDO have been studied in the solvents nitromethane and dioxane. For the solution in nitromethane to the upper limit of solubility of water (about 7 mol%) and in dioxane to a concentration of about 60 mol% the exchange remains rather slow. At higher concentrations the rate of exchange in dioxane increases rapidly with water concentration, indicating the promotion of the exchange via large water clusters. The isotope shift Deltadelta = delta(HDO) - delta(H2O) appears to be dependent on the concentration of water in the solvent, and an equation describing this dependence is proposed.