Micelle catalyzed oxidative degradation of norfloxacin by chloramine-T

Present work reports influence of micellar media (CTAB) upon the oxidative degradation of fluoroquinolone family drug norfloxacin (NOR). The reaction has been studied at constant temperature (308 K). The stoichiometry of the reaction was found to be 1:4 and oxidation products were identified by LC–MS technique and other spectral studies. The reaction exhibited first-order-dependence on chloramine-T [CAT] and fractional-order dependence on [NOR]. The rate constant was independent of cationic micelles of cetyltrimethylammonium bromide [CTAB] at lower concentrations followed by a rapid increase in rate constant to a maximum and further gradual decrease in rate constant at higher CTAB was observed. In the presence of CTAB, both the oxidant and substrate are distributed between the aqueous and the micellar pseudo phases and then react to give the product. Compensation between water structure destruction and substrate–micelle interaction plays an important role in the presence of CTAB. The rate constants were obtained and the applicability of Piszkiewicz's, Raghvan–Srinivasan's and pseudo phase models allowed us to obtain the reactivity constants in the aqueous pseudo phase and in the micellar pseudo phase (k2w and k2m) and the binding constants of the reactants to the micellar phase (K1, K2). The effects of inorganic salts i.e. [SO42−], [HSO4−], [Cl−] and [Br−] on reaction rate have also been studied.

Graphical abstractThe different reactivities of the reactants present in the two pseudo phases can be defined using the corresponding second order rate constants k2w (rate constant in aqueous pseudo phase) and k2m (rate constant in micellar pseudo phase) and are portrayed in figure.Figure optionsDownload full-size imageDownload high-quality image (54 K)Download as PowerPoint slideHighlights► Extensive kinetic and mechanistic study has been done to elucidate the fate of degradation of Norfloxacin during chlroination process. ► Catalytic role of cationic surfactant CTAB in the reation has been explored. ► Various models have been applied to ensure the catalytic role of CTAB.