Kinetics and mechanism of single electron oxidations of the tervalent uranium ion, U³⁺(aq), by free radicals in aqueous solutions

The specific rates of oxidation of U³⁺(aq) by OH^., Cl₂^.-, Br₂^.-, I₂^.-, (NCS)₂^.-, ^.CH₂CO₂H, ^.CH(CH₃)CO₂H, ^.CH₂C(CH₃)₂OH, and ^.CH₃ are reported. The results are interpreted as indicating that all these reactions occur via an inner-sphere mechanism with an increase in co-ordination number. This conclusion contradicts earlier suggestions that oxidations of aqua complexes by OH^. radicals proceed via hydrogen-atom abstraction from one of the aqua ligands. The specific rate of the reaction U³⁺(aq) + H₂O₂ is estimated to be 2 × 10⁵ dm³ mol^-1 s^-1.