Oxidation process and kinetics of bromothymol blue by alkaline permanganate

Abstract

AbstractSpectrophotometric analysis was applied to check the kinetics of bromothymol blue (BTB) oxidation by alkaline permanganate at constant ionic strength 0.2 mol dm−3. The redox reaction was observed to proceed through two independently distinct, detectable steps. The first step coexists with the formation of intermediate complexes involving transient species relatively quickly of the blue hypomanganate(V) and green manganate(VI). The slowly decomposed intermediate formed to produce soluble colloidal manganese(IV) and the BTB keto‐derivatives as second slow‐stage oxidation products. The oxidation reaction demonstrated first‐order dependence in [MnO4−] and fractional first‐order kinetics at each of the BTB and alkali concentrations at an initial rapid stage for complexes formation. It was found that the oxidation process is of a base‐catalyzed nature. Novel spectrophotometric measurement of the blue hypomanganate(V) was introduced using a traditional spectrophotometer. An effective oxidation mechanism compatible with the kinetic data obtained in terms of the activation parameters assessed was analyzed, proposed, and discussed in line with the kinetic findings.