Kinetic electron paramagnetic resonance study of the reactions of t-butylperoxyl radicals in aqueous solution

Abstract

The kinetics of reactions of t-butylperoxyl radicals in aqueous solution have been measured using electron paramagnetic resonance, ultraviolet absorption spectroscopy and gas chromatography. The rate constants for the overall self-reaction, the separate terminating and non-terminating reactions are very similar to those observed in non-polar solvents and the gas phase. The t-butoxyl radicals, formed by the non-terminating reaction, can either undergo scission, which leads to methylperoxyl radicals, or react with further t-butyl hydroperoxide to regenerate t-butylperoxyl radicals. The cross-termination reaction between methylperoxyl and t-butylperoxyl radicals is an important route in the overall termination sequence. The propagation reaction occurs significantly only at high concentrations of t-butyl hydroperoxide, ([ButOOH] > 0.3 mol dm^–3) and its rate constant is much lower than that in non-polar solutions.