The kinetics of the oxidation of hydrazoic acid by aquocerium(IV) ions in aqueous perchlorate media

Abstract

The rapid reaction of Ce^IV with hydrazoic acid in perchlorate media has been followed by use of the stopped-flow technique. Oscilloscope traces show a rapid rise in optical density followed by a slower, but still rapid, decay: the rise is ascribed to the formation of Ce^IV–hydrazoic acid complexes, and the decay to the oxidation of hydrazoic acid. A detailed kinetic study of the latter reaction shows that it is of the first order in [Ce^IV] and zero order in both [H⁺] and [HN₃]: the consumption ratio Δ[Ce^IV]/Δ[HN₃]= 1·0. These kinetic orders contrast with those found for the oxidation of hydrazoic acid by other cations, and they are discussed in terms of mechanisms involving hydrazido- and azido-complexes. The low value for the activation energy contrasts with the values obtained for the oxidation of hydrazoic acid by other cations.