The Kinetics of Complexed and Free Ho₂ Radical in the Reaction of Ce⁺⁴ and H₂O₂

The intermediates formed in the reaction of Ce⁺⁴ with H₂O₂ in 0.5 M perchloric acid were studied, spectrophotometrically and through the quenching method, using a stopped‐flow system. The spectrum in the UV range and the kinetics of the generated radicals and their dependence on Ce⁺³ concentration were investigated. On adding Ce⁺³ to the mixture, a change in the spectrum as well as in the recombination rate constant was observed. This behaviour was attributed to the formation of a complex between the cerous ion and the HO₂ radical. The values of the recombination rate constant of the complexed radical is 4.0 ± 0.4·10⁶ F⁻¹ sec⁻¹ while that of the free HO₂ radical is 0.9 ± 0.1·10⁶ F⁻¹ sec⁻¹. The stabilization constant of the complex was found to be 60 ± 18 F⁻¹.