Bromine-Hydrolysis Control in the Cerium Ion-Bromate Ion-Oxalic Acid-Acetone Belousov-Zhabotinskii Oscillator

Article abstract of DOI:10.1021/j100263a026

Chemical oscillations in reacting systems containing BrO3(1-) have been interpreted as a switching phenomenon in which control of the overall reaction is passed back and forth between a set of radical reactions, whose major effect is the removal of Br(1-).Control switches to the radical reactions when is driven low enough.Oscillation occurs because Br(1-) is an indirect product of the radical reactions, causing control to be returned to the nonradical reactions.Bromide ion control of BrO3(1-)-driven oscillations has been challanged on the basis that in some systems the usual source of Br(1-) from the radical reactions is absent.It has been suggested that the oscillations are fact Br2 controlled.It is shown here that one of these puzzling oscillators can be simulated as Br(1-) controlled.By implication the others also can be.Bromine is an important intermediate in these systems as the controlling Br(1-) comes from Br2 hydrolysis and is in equilibrium with Br2 and HOBr.We call such an oscillator Br2-hydrolysis controlled.The simulation is based on 31 elementary reactions of which 9 are reversible.It was constructed on the basis of a large number of experiments on simpler, nonoscillatory reactions involving the same reactants and is much simpler than the mechanism of other BrO3(1-)-driven oscillators because of the relative simplicity in it of the reactions of oxalic acid and acetone.The rate constants thus determined were used without modification to obtain an essentially quantitative simulation of the oscillatory system.It is thus the most complete and quantitatively accurate simulation of a BrO3(1-)-driven oscillator with an organic substrate yet carried out.The complete mechanism can be reduced to a simple five-variable Oregonator-like model that contains no expendable stoichiometric factor and whose rate parameters all can be related directly to the concentration of a principal reactant.