Chemical Oscillations With Sodium Perborate as Oxidant

The peroxo compounds H ₂O ₂ and K ₂S ₂O ₈ represent one of the major constituents in many oscillatory chemical systems. In this contribution we demonstrate that beside H ₂O ₂ and S ₂ ${\text{O}}_8{}^{2-}$ the sodium perborate (NaBO ₃·H ₂O) can act as alternative oxidizing agent in oscillatory reactions. So far the H ₂O ₂ has been successfully substituted with NaBO ₃ in two oscillators: in the BO ${}_3^{-}$ –S ₂ ${\text{O}}_3{}^{2-}$ –Cu(II) flow system potential and pH oscillations, in the strongly alkaline Cu(II)-catalyzed BO ${}_3^{-}$ –SCN ⁻ batch reaction, which are rather different in their chemistry and dynamics, potential oscillations were observed. In spite of the significant differences in the oxidizing nature of H ₂O ₂ and NaBO ₃ we assume that the oscillatory cycle in the BO ${}_3^{-}$ –substrate and in the H ₂O ₂–substrate systems is similar in many aspects, therefore the numbers of this new subgroup of the oscillators may be considered to be borate-mediated H ₂O ₂ oscillators. Mechanisms are suggested and simulations are shown to describe the oscillatory behaviors observed in the perborate chemistry based oscillators by using the assumption that the oxidation reactions of the intermediates (HO) ₃B(OOH) ⁻ and (HO) ₂B(OOH) ${}_2^{-}$ anions, which are dominant species in alkaline and neutral pH solutions of perborate, are much faster than that of H ₂O ₂.