The chemistry of vitamin B12. Part 23. Decomposition of the cobalt(I) cobalamin B12s in aqueous solution; a novel oscillating reaction

Abstract

The decomposition of ca. 3 × 10^–5 mol dm^–3 aqueous solutions of the cobalt(I)(B_12s) to the cobalt(II)(B_12r) cobalamin under nitrogen has been studied at 36 °C by u.v.–visible spectrophotometry. The reaction shows marked oscillations in the relative concentrations of the cobalt(I) and cobalt(II) complexes with good isosbestic points and no evidence for the occurrence of any spectroscopically distinct intermediate. The oscillations appear to consist of a basic train with a period of 4–5 min and one or more superimposed trains. The oscillations are destroyed by light and the period decreases with increasing temperature, but the reaction is relatively unaffected by other variables such as pH (2–12).