Osmium tetroxide catalyzed oxidation of mefenamic and tolfenamic acids with alkaline chloramine-B: Delineation of kinetic, mechanistic and catalytic chemistry

Abstract The kinetic oxidation of mefenamic acid (MEF) and tolfenamic acid (TOL), which therapeutically belongs to the class of non-steroidal anti-inflammatory drugs (NSAIDs) finds extensive applications in pharmaceuticals. The kinetics of oxidation of MEF and TOL by chloramine-B (CAB) in the presence of osmium tetroxide (OsO 4 ) catalyst has been investigated at 313 K in alkaline medium. The oxidation behavior of these two drugs is similar with a first-order dependence of rate on both [CAB] 0 and [OsO 4 ] and a negative-fractional-order dependence on [NaOH]. The order with respect to [Drug] 0 is zero. The dielectric effect is negative. Activation parameters have been evaluated for the composite reaction as well as with respect to catalyst. The oxidation products were characterized by GC–MS analysis. The observed experimental results have been justified by a plausible reaction mechanism. The relevant kinetic rate laws have been deduced.