Role of surfactants on Fe(II) catalyzed L-tryptophan oxidation by persulfate

Abstract

The present study aims to explore the kinetics of Fe(II) catalyzed L-tryptophan (Trp) oxidation in micellar media by persulfate ion (S2O8 2–). The reaction's progress has been analyzed as an indicator of [S2O8 2–], temperature, [Trp], [Fe(II)], [Surfactant], ionic strength, and [H+]. The S2O8 2– undergoes a 1:1 stoichiometric interaction with Trp. The observed reaction exhibits first-order kinetics with regards to [S2O8 2–], fractional-first-order with respect to [H+], linear reliance to [Fe(II)], and invariance with respect to [Trp] within the range of concentrations investigated. The observed decrement in reaction rate upon electrolyte introduction is suggestive of a negative salt effect. The oxidation rate is significantly enhanced by Fe(II) solution (as a catalyst) at lower concentrations. Both the cationic cetyltrimethylammonium bromide (CTAB) and the anionic sodium dodecyl sulfate (SDS) have been shown to inhibit the oxidation rate, while the non-ionic Triton X-100 (TX-100) does not have a noticeable impact on the reaction rate.