Role of Surfactants on Fe(II) catalyzed L-Tryptophan Oxidation by Persulfate

Abstract

The proposed study aimed to explore the kinetics of Fe(II) catalyzed L-Tryptophan (Trp) oxidation in a micellar media by persulfate ion (S₂O₈^2-). The reaction's progression was 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’s 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) were shown to inhibit the oxidation rate, while the non-ionic Triton X-100 (TX-100) did not have a noticeable impact on the reaction rate.