Electron spin resonance kinetic studies of malonyl radical self-decay and oxidation reactions by cerium(IV) and bromate in acid aqueous media. The role of free radicals in the Belousov-Zhabotinskii oscillator

Abstract

Kinetics of selected reactions involving malonyl radicals (M), generated by Ce(IV) oxidation of malonic acid in acid aqueous media, have been studied by steady-state electron spin resonance under stopped-flow conditions. Rate constants for second-order radical self-decay, k_2(M+M) = 3.2 x 10^9, oxidation by bromate, k_4(M+BrO_3^-) = 6.7 x 10^3, and an upper limit for its oxidation by Ce(IV), k_3(M+Ce(Iv)) ≤ 1.2 x 10^5 M^(-1) s^(+1), have been obtained at 298 K. Some of the consequences of the present results on the mechanism of the Belousov-Zhabotinskii oscillator are examined.