Electrophilic Displacement Reactions. XI. Solvent Isotope Effects in the Protodeboronation of Areneboronic Acids

The effect of solvent hydrogen isotope composition (hydrogen and deuterium) on the rates of protodeboronation of p-methoxybenzeneboronic acid in 6.3 M sulfuric acid and of 2,6-dimethoxybenzeneboronic acid in 0.1 M perchloric acid were studied. In the former case k/sub H//k/sub D/ is 3.7 and the rate constant vaniation with solvent isotope composition is nearly linear. In the latter case k/sub H//k/sub D/ is 1.7 and variation of rate constant with solvent isotope composition is non-linear. This rate behavior is in quantitative accord with that expected for a rate-determining proton transfer. (auth)