STOICHIOMETRY AND KINETICS OF MANGANESE(3) REACTIONS WITH HYDROXYLAMINE O-METHYLHYDROXYLAMINE AND NITROUS ACID IN ACID PERCHLORATE SOLUTION

The stopped-flow apparatus has been used to determine the kinetics of reaction between manganese(III) and the reductants NH3OH+,NH3OCH 3, and HNO2 at 25° in acid (0.50-3.70 M) perchlorate media. Nitrate was determined as a product of oxidation of hydroxylamine. Stoichiometric measurements with Mn(III) in excess were used to analyze the kineticdata with excess of substrate in terms of the reactions [formula omitted].All reactions were second order over-all, and first order in each reactant. The reactions were also independentof initialconcentration of reactants,[Mn2+] [NaClO4], [NaNO3], ionic strength, and wavelength. The observed rate constant was dependent on acidity. A mechanism consistent with these results was postulated, in which the rate-det rmining steps involve the formation of the NH2O., NHOCH3, and NO2 radicals for the reactions with NH3OH-, NH3OCH3, and HNO3, respectively. The acidity dependence arises from reaction with Mn3+ and MnOH2+. With the primed rate constant designating MnOH2+ reaction, the rate constants for the rate-determining steps are:[formula omitted]. The relative slowness of the reaction with NH3OCH3 is ascribed to the lack of hydrogen bonding in this system. © 1969, American Chemical Society. All rights reserved.