Several carbonyl group reactions which involve rate-determining proton transfer between electronegative atoms, as evidenced by biphasic Bronsted plots and detailed kinetic analysis, also give kinetic hydrogen isotope effects which change rapidly with the pKa difference between the proton donor and the protonated proton acceptor (ipK) and peak sharply at LpK=O. This indicates that the proton transfer component of the overall proton transfer process (encounter of reactants, proton transfer, and

more »

... paration of products) is at least partly rate-determining in these systems, but it is so only over a narrow region of ipK about tpK=O. Kinetic isotope effects on the basecatalyzed decomposition of nitramide as well as the shape of the Bronsted plots for this reaction and the deprotonation of the conjugate acid of 2, 7-dimethoxy-l, 8-bis(dimethylamino)naphthalene indicate that proton transfer involving nitrogen is intrinsically slower than that involving oxygen and is therefore (partly) ratedetermining over a wider, albeit still rather limited, range of LpK.