Oscillatory reactions classification

Classification of oscillations in chemical systems will be made in terms of three groupings chemical reactions, chemical elements, and oscillatory mathematical solutions. In the first grouping an enumeration of different reactions , are considered. In the second, a listing of those chemical elements which take part in oscillatory reactions are considered. Finally, the oscillatory solutions of the mathematical model represented by the rate equations are classified on the basis of known examples. 

The pathway from Ce + to Br is the key to negative feedback on HBr02, which helps to remove this species after being accumulated due to autocatalysis. However, different roles are associated with the two species while Br is an inhibitor that directly removes HBr02, Ce" " " is a controlling species that provides a delay allowing the autocatalysis to advance considerably before inhibition by Br causes the concentration of HBr02 to drop hence oscillations may appear. As before, proper time scales of reaction steps are necessary for oscillations to appear. Clearly, this example of isothermal oscillations is more involved than the thermokinetic one. In particular, there are three main (or essential) types of variables rather than two this observation prompts for a classification of oscillatory reaction mechanisms—one of the main topics of this chapter. 

In order to form a bridge between the laboratory (chemical) experiments and the theoretical (mathematical) models we refer to Table I. In a traditional approach, experimental chemists are concerned with Column I of Table I. As this table implies there are various types of research areas thus research interests. Chemists interested in the characteristics of reactants and products resemble mathematicians who are interested in characteristics of variables, e.g. number theorists, real and complex variables theorists, etc. Chemists who. are interested in reaction mechanism thus in chemical kinetics may be compared to mathematicians interested in dynamics. Finally, chemists interested in findings resulting from the study of reactions are like mathematicians interested in critical solutions and their classifications. In chemical reactions, the equilibrium state which corresponds to the stable steady states is the expected result. However, it is recently that all interesting solutions both stationary and oscillatory, have been recognized as worthwhile to consider. 

When set up appropriately, autocatalytic chemical reactions (taking the usual meaning of the term) frequently give rise to a "bistability" (in particular bistationarity), and chemical hysteresis as its corollary. Since these reactions are relatively well documented elsewhere, it does not appear necessary to list them all there, particularly since they are quite numerous. Conversely, oscillatory chemical reactions in homogeneous chemical media are rather rarer and, apart from two exceptions, have recently been discovered. Since there is no satisfactory criterion permitting the classification of chemical oscillators at present, we can do little more than record them in a somewhat arbitrary order ... 

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