Kinetic and mechanistic study of oxidation of l-methionine by Waugh-type enneamolybdomanganate(IV) in perchloric acid

Abstract

The reaction between methionine and enneamolybdomanganate(IV) in perchloric acid was carried out under pseudo-first-order conditions keeping large excess of methionine. The orders in oxidant and substrate were found to be unity and 0.91, respectively. The reaction proceeds with rapid formation of complex between the reactants followed by its decomposition in a rate determining step. The accelerating effect of hydrogen ions on the reaction is due to the formation of active hexaprotonated oxidant species. The product of the reaction was found to be methionine sulfoxide. The reaction involves direct two-electron transfer step without any free radical intervention. The effect of ionic strength, solvent polarity and the activation parameters were also in support of the mechanism proposed.

Kinetics and Mechanism of Oxidation of Glutahione by Waugh‐Type Enneamolybdomanganate(IV) in Aqueous Perchloric Acid

“…[23] The oxidant was characterized by Fourier-transform infrared spectroscopy and AAS analysis as reported earlier. [24,25]…”

Oxidation and Reduction

“…The proposed mechanism suggested a rapid formation of a complex by the reactants, which suffered two-electron transfer and decomposed in the rate-determining step. 117 The [Co(III)Mo 6 O 21 ] 3− ion oxidation of ethanediol to HCHO in H 2 SO 4 -H 2 O was first order in oxidant and substrate. The rate acceleration by H + ion was attributed to the protonation of the complex.…”

Kinetics and mechanism of oxidation of pyridoxine by enneamolybdomanganate(IV)

“…Molybdenum, the major content of the oxidant used, is found in several tissues of the human body and is required for the activity of xanthine oxidase which is involved in the catabolism of purines [15]. In continuation of our earlier studies [6,7,16,17], oxidation of vitamin B6 by enneamolybdomanganate(IV) was carried All chemicals were of reagent grade and double-distilled water was used throughout the work. A solution of pyridoxine hydrochloride (vitamin B6)(Hi Media) was freshly prepared by dissolving an appropriate amount of sample in double-distilled water.…”

“…The ammonium salt of Mn IV complex, (NH 4 ) 6 [Mn IV Mo 9 O 32 ] was prepared by reported method [18]. The oxidant was characterized by FTIR and AAS analysis as reported earlier [16,17].…”