The oxidation of hypophosphite and phosphite by the Anderson‐type hexamolybdocobaltate(III), [H6CoIIIMo6O24]3−, anion was investigated at pH 2 and 1, respectively, in aqueous medium. The reaction is found to occur through an outer‐sphere mechanism with a prior weak complex formation between the reactants. Under the reaction conditions, the oxidant exists in the [H5CoIIIMo5O20]2−, [H6CoIIIMo6O24]3−, and [H4CoIII2Mo10O38]6−(dimer) forms, and [H5CoIIIMo5O20]2− is the active species. Inhibition of the reaction by the oxidant anion and added molybdate ion kinetically indicates existence of prior equilibria between various forms of the oxidant. Both hypophosphite and phosphite exists in their protonated forms. The reaction involves direct electron transfer from the phosphorus center to the anion‐generating free radicals in a rate‐determining step. The effect of ionic strength and change in the solvent polarity did not affect the rate of the reaction. A probable mechanism was proposed leading to a complicated rate law as a result of involvement of prior equilibria between various forms of the oxidant. The activation parameters were also determined and are in support of the proposed mechanism.
ABSTARCTThe reaction between hydroxyl amine and Waugh-type polyoxometalate, enneamolybdomanganate(ΙV), was investigated under pseudo-first-order condition in aqueous perchloric acid. The product of the reaction was nitrous oxide as determined by studying the stoichiometry which requires one mol of oxidant per mole of hydroxylamine. The rate of reaction increases as hydrogen ion and oxidant, enneamolybdomanganate(ΙV), concentrations increase, while it remains unchanged as the hydroxylamine concentration is altered. The oxidant exists in both protonated and unprotonated form under the reaction conditions and both are active. The hydroxyl amine remains in the protonated form and reacts with the active forms of the oxidant with different rate constants. The proposed mechanism, in accordance with the kinetic results obtained, involves reaction between hydroxyl amine and oxidant in a slow step. The rate law derived as per the proposed mechanism is also verified kinetically. Change in ionic strength and solvent polarity did not affect the rate of the reaction while activation parameters were calculated by studying the reaction at different temperatures
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.