Kinetics of protolytic and keto–enol reactions of some 5-monosubstituted barbituric acids

Abstract

We have determined the relaxation times in the millisecond range of barbituric acids with the 5-substituents H, methyl, ethyl, isopropyl, and phenyl in aqueous solution as a function of temperature. The kinetic parameters of protolysis and keto–enol interconversion have been evaluated. The influence of the substituents on these parameters can be explained more satisfactorily by the influence of the structure of solvent water rather than by the inductive effect.