The role of intermediate oxidation states of technetium in catalysis of the oxidation of hydrazine by oxo-anions. Part 1. Nitrate ions

Abstract

The catalysis by technetium of the oxidation of hydrazine by nitric acid has been studied over a wide range of concentrations of hydrazine and nitric acid and also in media where HNO₃ is replaced by HBF₄. The reaction is confirmed as a chain process, exhibiting a higher turnover number of hydrazine molecules per atom of Tc and a kinetic profile consisting of an initial slow stage, a very fast stage and a termination stage characterised by a high residual concentration of unreacted hydrazine and the existence of all Tc in the form of the initial pertechnetate ion. A model of the reaction which is an elaboration of that devised earlier by Garraway and Wilson, reproduces the main characteristics of reaction over a much wider range of reactants than before. The strong effects of increasing the acid concentration are in the opposite direction for HNO₃ and HBF₄.