Novel methods for determining substrate basicity properties and kinetic parameters from kinetic data for reactions in strong acid solutions

Abstract

Many compounds react in strong mineral acid solutions by fast equilibrium protonation followed by a slow, rate-determining reaction of the cation. In mechanistic studies involving the variation with acidity of the rates of such reactions it is necessary to separate the effect of changing acidity on the reactivity of the cation from its effect on the amount of cation present. This latter factor is normally studied by a static determination of the compound's basicity. We now show that such determinations can be unnecessary, and that suitable treatment of plots of kinetic data against acidity can define both the static basicity behaviour of the compound and the kinetic behaviour of the cation. These novel methods have been applied to existing kinetic data for cyclohexadienone rearrangements and for amide hydrolyses. For the latter, a mechanism involving reaction through a single, most abundant, cation gives excellent correlation with the experimental results.