Mechanism of B-Z reaction positive and negative feedback

In this section, we will comment on the broad features of the mechanism of B-Z reaction. As we have seen in an oscillatory reaction system, number of components, by-products and intermediates (including free radicals) are involved which can yield numerous possible reaction steps. Hence, deciphering of mechanism is quite complicated. For example, in Gyorgyi, Tura nyi, Feild (GTF) model, the number of postulated reactions steps is 80, involving 26 reactants [25]. However, all the steps involve electron-transfer and free-radical reactions. 

In the case of oscillatory reaction under discussion, reactions are ionic in nature and oscillating species are ions. The oscillating species Br and Ce +/Ce + are detected by bromide and platinum sensitive electrodes in conjunction with standard calomel electrode. The essential challenging task of developing a reaction mechanism is to postulate how the concentration of Ce + and Br builds-up in the course of time and how it is periodically inhibited. In the light of Brusselator model discovered by 

Prigogine and co-workers in 1968, build-up is supposed to be due to autocatalysis of some species produced in the reaction and decay is related to destruction of the growth of autocatalysed species by another reaction. Hence, the first step needed for suggesting a plausible mechanism involves identifying (i) the autocatalytic step and the species being autocatalysed (ii) the inhibitory step (iii) steps involved in the generation of species which initiate the autocatalytic reactions and (iv) step involved in the removal inhibitor. 

It is easy to visualize it in terms of population dynamics in case of chemical reactions, it is somewhat difficult to conceive but it can be visualized that it involves a combination of steps of the following type  

The real problem arises in identifying these two steps. 

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