Equilibrium isotope effects on the proton transfer reactions of methylbenzenes

The results obtained show that the equilibrium constant for the proton transfer equilibrium in p-xylene and p-xylene-d/sub 6/ is in the range 0.85 to 1.00. Uncertainties in the equilibrium constant measurement result from uncertainties in the degree of insufficient deuteration; if the correction for insufficient deuteration is ignored, the importance of the proton transfer to the undeuterated species will be overestimated. The isotope effect on the proton transfer reaction, if it exists, is small (approximately 0.05 kcal/mole). (LK)