Resumen

SRIVASTAVA, Abhishek; MANJUSHA; SRIVASTAVA, Neetu  y  NAIK, Radhey Mohan. Kinetic Study of Ru(III) Promoted Oxidation of L-Tryptophan in an Anionic Surfactant Medium by Hexacyanoferrate(III). J. Mex. Chem. Soc [online]. 2023, vol.67, n.1, pp.46-59.  Epub 11-Mar-2024. ISSN 1870-249X.  https://doi.org/10.29356/jmcs.v67i1.1829.

The kinetic investigation of Ru(III) promoted oxidation of L-tryptophan (Trp) by [Fe(CN)6]3- has been performed in anionic sodium dodecyl sulfate (SDS) micellar medium by recording the decrease in absorbance at 420 nm, corresponding to [Fe(CN)6]3- using UV-visible spectrophotometer. Pseudo-first-order condition has been used to examine the progress of reaction as a function of [Fe(CN)6 3-], ionic strength, [OH-], [SDS], [Ru3+], [Trp], and temperature by changing one variable at a time. The results exhibit that [OH-], [SDS], and [Trp] are the decisive parameter showing an appreciable effect on reaction rate. The reaction exhibits first- order kinetics in the studies concentration range of Ru(III), [Fe(CN)6]3- and at lower [Trp] and [OH-]. The incremental trend observed in the reaction rate with electrolyte concentration shows a positive salt effect. The reaction rate is almost ten times faster in SDS micellar medium compared to the aqueous medium. [Fe(CN)6]3- does not show any appreciable effect on the critical micellar concentration (CMC) of SDS as the polar head of SDS and [Fe(CN)6]3- both are negatively charged. The K+ obtained from K3[Fe(CN)6] and KNO3 decreases the repulsion between the negatively charged heads of the surfactant molecules thereby decreasing the CMC of SDS. The activation parameters also support the outer-sphere electron transfer mechanism as proposed by us.

Palabras llave : Critical micellar concentration; surfactant; L-tryptophan; activation parameters; kinetics and mechanism; hexacyanoferrate(III).

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