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

Abstract

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.