Kinetic study of Ru(III) – catalyzed oxidation of L-phenylalanine by hexacyanoferrate(III) in an anionic surfactant medium
Abhishek Srivastava, Ruchi Singh, Neetu Srivastava, Radhey Mohan Naik
Abstract
Abstract The kinetic investigation of Ru(III) promoted oxidation of L-phenylalanine (L-PheAla) 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 an UV–visible spectrophotometer. Using the pseudo-first-order condition, the course of the reaction was studied as a function of [Fe(CN) 6 3− ], ionic strength, [OH − ], [SDS], [Ru 3+ ], [L-PheAla] and temperature by changing one variable at a time. The results exhibit that [OH − ], [SDS], and [L-PheAla] are the crucial parameters that have an appreciable influence on the reaction rate. The reaction exhibits first-order kinetics in concentration ranges of Ru(III), [Fe(CN) 6 ] 3− and at low [L-PheAla] and [OH − ] concentrations. The incremental trend observed in the reaction rate with electrolyte concentration shows a positive salt effect. The reaction rate is almost 10 times faster in SDS micellar medium than in aqueous medium. [Fe(CN) 6 ] 3− has no appreciable effect on the CMC of SDS, since the polar head of SDS and [Fe(CN) 6 ] 3− are both negatively charged. The K + obtained from K 3 [Fe(CN) 6 ] and KNO 3 decreases the repulsion between the negatively charged heads of the surfactant molecules, which decreases the CMC of SDS. The activation parameters also support the outer-sphere electron transfer mechanism.