Oxidation of ferrous ions by hydroxyl radicals

Abstract

Hydroxyl radicals have been found by pulse radiolysis to oxidize hydrated ferrous to ferric ions with a rate constant of (2.3 ± 0.2)× 10⁸ M^–1 s^–1. The corresponding reaction of OD radicals in D₂O solution has a rate constant of (9.4 ± 0.8)× 10⁷ M^–1 s^–1. OD radicals oxidize ferrocyanide in D₂O solution with (9.7 ± 1.0)× 10⁹ M^–1 s^–1. The mechanism of the oxidation of ferrous ions is though to consist of simple electron transfer, and the difference in rate between H₂O and D₂O solution is attributed to differences between free energies of hydration in the two solvents.