Catalytic oxidation of p-nitrodiphenylamine with peroxydisulphate in micellar and non-micellar media

Department of Chemistry, Faculty of science, Tanta University, Tanta, Egypt.

Abstract

The kinetics of oxidation of p-nitrodiphenylamine (p-NO²-DPA) with the peroxydisulphate ion has been investigated spectrophoto-metrically. The uncatalyzed oxidation process was so slow but was accelerated tremendously upon the incorporation of Ag⁺ as catalyst. At moderate concentration of the catalyst, the reaction proceeds with first order kinetics with respect to the substrate, oxidant and catalyst concentrations. In the presence of high concentration of Ag⁺, the order of reaction for the substrate species turned to zero, resulting in an overall second order reaction consisting of first order kinetics for the Ag⁺ and S₂O₈^2- individually. Sodium dodecyle sulphate (SDS) micelles showed further enhancement in the catalyzed reaction rate when its concentration was ≤ 3 x 10^-3 M. Above this limit an inhibition occurred. Such enhancement has not been observed with cetyltrimethylam-monium bromide (CTAB) but only a retardation was observed. Mixed solution of both SDS and CTAB also inhibited the rate considerably. Mechanisms describing the oxidation processes have been suggested.