A mechanistic study of some redox reactions of nitrogen (III)

Abstract

Oxidation of nitrogen(III) by chlorite, periodate and chlorate is reported in this work.

The introduction reviews the reported, assumed and proposed reactivities of non-metallic oxyanions in aqueous acid solutions in general and the reactants studied in the present investigation in particular.

Mechanistic studies of the reactions, N(III)/C1(III) and N(III)/I(VII) are reported for the first time.

Nitrite and chlorite react under mildly acid conditions (pH ∼ 4) in the molar ratio of 2:1. The rate equation is represented by, Rate = [NO ₂-]1.5[ClO_2-] 0.5[H+]1.5(k + k'[Cl-]). The reaction between nitrite and periodate has been studied in aqueous hydrochloric acid solution (pH ∼ 0). Its rate equation is represented by, Rate = k[HNO ₂]0.5[H₅IO₆][H+]Cl -][Br-]. The rate of reaction is particularly catalysed by traces of Br-. This observation may nominate the reaction as the simplest method that may be used for the quantitative estimation of traces of Br- present in chlorides.

In a rather differently oriented study, the reaction between N(III)/C1(V) has been studied in water/dioxan solutions. The specific rate constant for the reaction increases as the dielectric constant of the medium decreases, a result which agrees with the mechanism suggested by other workers. The ionization constants of nitrous acid in similar water-dioxan mixtures are also reported.