Metal-ion oxidations in solution. Part VII. Oxidation of bromide by cobalt(III)

Abstract

The cobalt(III) oxidation of bromide has been studied in the range 2–15° by the stopped-flow technique. In the acidity range 0·24–0·40M, the reaction has been shown to be second order, and is consistent with a mechanism both the cobalt(III) ion and its corresponding hydroxy-complex: Co³⁺+ Br^– [graphic omitted] Co^II+ Br˙, CoOH²⁺+ Br^– [graphic omitted] Co^II+ Br˙, 2Br˙ [graphic omitted] Br₂ The rate constants k₁ and k₂ are 4·5 ± 1 and 770 ± 90 M^–1 sec.^–1 respectively at 7·5°, the associated activation energies being 22 ± 4 and 10 ± 3 kcal./mole. The reaction is considered to involve an S_N1 process followed by the very fast redox step.