Abstract

J. N. Barge and G. S. Gokavi

DOI : http://dx.doi.org/10.13005/ojc/330554

The reaction between hydroxyl amine and Waugh-type polyoxometalate, enneamolybdomanganate(IV), 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(IV), 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.

Polyoxometalate Oxidation; Reaction Mechanism; Enneamolybdomanganate; Hydroxylamine

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