Conclusive evidence for delayed autocatalytic behavior of Mn(II) ions at a critical concentration

Abstract

The kinetics of the permanganic oxidation process of glycine, L-alanine and L-leucine in strong acid media were investigated using a spectrophotometric technique. Conclusive evidence has proven that the autocatalytic activity of Mn(II) in these reactions in strong acidic media is analogous to that of weak acid media, but in the former, Mn(II) ions should acquire a critical concentration for them to show autocatalytic characteristics. This critical concentration depends on the nature of the amino acid used. Considering the delayed autocatalytic behavior of Mn(II) ions, we herein present the rate equations and mechanisms satisfying observations for both catalytic and noncatalytic routes. The correspondence of the pseudo-order rate constants of the catalytic and noncatalytic pathways to Eyring law verify both the critical concentration as well as the delayed autocatalytic behavior concepts. In general, the onset of delayed behavior can be attributed to the concentration ratio of Mn(II) to amino acid which can be of a certain value for any particular amino acid.

Kinetics and Mechanism of Permanganate Oxidation of Clopidogrel Hydrogen Sulfate: An Antiplatelet Drug in Acid Perchlorate Solutions

“…Complex formation was also confirmed kinetically with a Michaelis–Menten plot (Figure b). The probable structure of the complex C isSuch complex formation between substrate and oxidant has also been reported in the literature. , …”

“…The probable structure of the complex C is Such complex formation between substrate and oxidant has also been reported in the literature. 15,16 Substituting eqs 8, 11, and 13 into eq 6 and omitting the subscripts, we have rate…”

Three Rate-Constant Kinetic Model for Permanganate Reactions Autocatalyzed by Colloidal Manganese Dioxide: The Oxidation ofl-Phenylalanine

“…An integrated rate equation that allows the determination of the two rate constants associated with the nonautocatalytic and autocatalytic reaction pathways has been reported. − However, some deviations from the proposed mathematical model are evident from the experimental kinetic data published for the permanganate-glycine reaction . Moreover, a case of delayed autocatalysis has been reported for the permanganate-amino acid reactions under acidic conditions. − Although delayed autocatalysis is not interpretable by the two rate-constant model, it has also been observed in at least another permanganate reaction . As a consequence, a new model has now been developed that allows the determination of three rate constants for each kinetic experiment.…”

Investigation of Hydrogen Oxidation/Evolution Reactions Based on Charge-Transfer Coefficients Derived from Butler–Volmer and Eyring Analyses

“…From the Eyring plots (log­( i k /T ) vs 1/ T ), the slope gives Δ H # and the intercept yields the log ( A f ). For chemical reactions, the Eyring equation is written in terms of log­( k/T ) vs 1/ T . ,,− However, for an electrochemical reaction, k is directly proportional to the i k ,,, and turnover frequency (TOF). , Hence, the Eyring equation can be written in terms of log­( i k /T ) vs 1/T. − …”