Nitrogen-Isotope Effects in the Reduction of Nitrate, Nitrite, and Hydroxylamine to Ammonia. I. In Sodium Hydroxide Solution with Fe (II)

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Abstract
Studies were made of the nitrogen‐isotope effects occurring during the alkaline reduction of NO3−, NO2−, and NH2OH with Fe(II). The pertinent reduction reactions were shown to be irreversible and the yields of NH3 quantitative. The reduction of NO3− to NH3 produced a k14/k15 value of 1.075±0.004 at 25°C. A k14/k15 ratio of 1.034±0.002 at 25°C was obtained for the reduction of NO2−, or NH2OH to NH3. The rate constant, kNO3−, was shown to be slow compared to kNO2− and kNH2OH which had values of 4.09×10−2 and 9.53×10−3 sec−1, respectively. The experimental data agreed well with results computed for a two‐atom model in which the significant step in the reduction of each species was the breaking of an N–O bond. Reactions consistent with the experimental data were proposed to account for the reduction mechanism.