Nonlinear Hammett relationships in the reaction of peroxomonosulfate anion(HOOSO3-) with meta- and para-substituted anilines in alkaline medium

The HOOSO3- oxidation of eleven meta- and para-substituted anilines to the corresponding nitrosobenzenes at pH approximate to 11 was characterized by the rate equation nu = kK[OX][An]/(1 + K[An]). Formation constant of the re active intermediate and its rate of decomposition were evaluated separately for ascertaining the structure-reactivity relationships. Under the experim ental conditions the dianion, O--O-SO3- is probably the effective electroph ile. Kinetic data can be rationalized by a bimolecular process which involv es the attack of nucleophilic nitrogen atom on the peroxidic oxygen. The hi ghlight of the study is the opposite curvatures observed in the nonlinear H ammett plots of first-order rate constant k and the "equilibrium" constant K, being concave downward and upward, respectively.