Kinetics and Stoichiometry of the Reduction of Hydrogen Peroxide by an Aminocarboxylactocobaltate(II) Complex in Aqueous Medium

Abstract

The kinetics and stoichiometry of the reduction of H2O2 by an aminocaboxylactocobaltate(II) complex (hereafter[CoHEDTAOH2] −) in aqueous medium have been studied under the following conditions: T = 29˚C ± 1˚C, Ionic Strength, I = 0.50 mol dm −3 (NaClO4), [H + ] = 1 × 10 −3 mol dm −3. The ratio from the stoichiometric study conforms to the equation 2[CoHEDTAOH2] − + H2O2 + 2H + → 2 [Co-HEDTAOH2] + 2H2O. The rate of reaction varied linearly to the first power of the concentrations of the reductant and oxidant and displayed inverse dependence on acid concentration. The plot of acid dependent rate constant versus [H + ] −1 was linear with zero intercept. The [CoHEDTAOH2] −-H2O2 reaction was insensitive to the change in ionic strength of the medium suggesting interaction of charged and uncharged species at the activated complex. The Michaelis-Menten plot of [ ] 1 1 1 versus k oxidant was linear without intercept which suggested absence of intermediate complex. Evidences in this paper showed that the reaction occurred through the outer-sphere mechanism.

Electrochemical Reaction in Hydrogen Peroxide and Structural Change of Platinum Nanoparticle-Supported Carbon Nanowalls Grown Using Plasma-Enhanced Chemical Vapor Deposition

“…In general, the reduction reaction of H 2 O 2 depends on the solution conditions. In an acid solution, H 2 O 2 is decomposed into H 2 O and O 2 [31]. On the other hand, it is known that anions (OH − ) are produced in neutral or alkaline solutions [32,33].…”

Electron transfer reaction of Tris(1,10-phenanthroline) cobalt(III) complex [Co(phen)3]3+ and thiosulphate ion (S2O32−) in an aqueous acidic medium

“…Where A∞ = final absorbance, at = absorbance at time t, A0 = Initial absorbance and k1 = pseudo-first order rate constant as reported elsewhere (Onu et al 2015, Ukoha et al 2015).…”

“…The effect of added ions on the reaction rate was observed by the addition of various amounts of ions (Mg 2+ , NH4 + , CH3COO -, HCOO -) while maintaining the concentrations of the complex, reductant and acid constant. The formation of free radical intermediates was detected by monitoring gel formation by acrylamide in partially reacted reaction mixture in excess methanol (Onu et al 2015).…”

“…, implicating a reaction process occurring via a single acid dependent pathway(Mshelia et al 2010;Onu et al 2015), thus the forward reaction in an equilibrium association of these active species becomes the rate determining step of the reaction in which an ion associate is formed (Equation 5). The concentration of the complex assuming a zero order with respect to the reaction, S2O3 2assuming a second order and the [H + ] taking up a first order was as a result of the equilibrium association of these species.…”

Kinetics of oxidation of ethylenediammine-N,N,N’,N’-tetraacetatocobaltate(II)complex by silver-activated persulphate ion in aqueous acidic medium

“…Thus, the study of oxidation of these complexes has continued to receive wide attention. Electron transfer reactions of these complexes with some oxyanions have been reported (Onu et al, 2008(Onu et al, , 2009(Onu et al, , 2015(Onu et al, & 2016Naik et al, 2007& Mansour, 2003. In these studies both the inner-sphere and outer-sphere mechanisms were reported.…”