Spectrophotometric Kinetic and Mechanistic Investigation of Chlorpromazine Radical Cation with Hexachloroiridate (IV) in Catalyzed Aqueous Acid Medium

Abstract

The kinetic mechanism of oxidation of Chlorpromazine (CPZ) (2-chloro-10-(3-dimethylaminopropyl) phenothiazine) by hexachloroiridate (IV) in acidic aqueous medium has been studied spectrophotometrically using UV-visible spectrophotometer at λ max 525 nm (ε, 10200 dm 3 mol À 1 cm À 1 ). The title reaction is overall second order being first order with respect to each reactant, but to be complicated at higher substrate concentrations. Oxidant has been found as strong electron transfer species to the formation of chlorpromazine radical cation and further respected sulfoxide. The rate also increases with increasing concentration of hydrogen ion and reaction is catalyzed by perchlorate medium. The oxidation is unaffected to variation in ionic strength. Various proposals have been suggested on the basis of reactivity of Ir [IV] and radical cation species. The activation parameters have been evaluated by employing Eyring equation. The oxidation product of CPZ has been confirmed spectrally and a suitable mechanism has been proposed.