Free-radical-induced oxidation of hydroxymethanesulfonate in aqueous solution Part 1A pulse radiolysis study of the reactions of OHand SO 4-

Abstract

The rate constants for the reaction of OH and SO₄^- with hydroxymethanesulfonate (HMS) have been determined. The hydroxyl radical was found to react with HMS by hydrogen abstraction to form CH(OH)SO₃^-, reaction (5), with a rate constant of (3.0±0.3)×10⁸ d mol^-1 s^-1. The spectrum of the product is dependent on pH due to equilibrium (6). This equilibrium has been investigated and has a pK_a of 6.35±0.1. The forward and reverse rate constants for the dissociation, k₆ and k_-6, are (5.9±0.5)×10⁴ s^-1 and (4.4±1.0)×10¹⁰ d mol^-1 s^-1, respectively. The dissociation is subject to acid–base catalysis by phosphate buffer, reaction (7), with k₇=(9.5±0.1)×10⁸ d mol^-1 s^-1 and k_-7=(1.32±0.02)×10⁸ d mol^-1 s^-1

The sulfate radical reacts with HMS with a rate constant of (1.3±0.2)×10⁶ d mol^-1 s^-1. The product of this reaction has not been identified.