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An overview of the brusselator, an autocatalytic, oscillating chemical reaction first described by ilya prigogine. The history of chemical oscillators, the behavior of nonlinear systems, and the importance of the brusselator in understanding these phenomena. It also includes the chemical equations and rate equations for the brusselator, as well as the conditions for oscillations.
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My Nguyen Dr. Reden Calculus Honors May 19th, 2016 Dynamical system project: Brusselator Chemical Oscillators have only been recognized as mainstream science since the 1960s. There was a prior belief that all chemical reactions progressed in one direction (monotonically) to equilibrium. First oscillating reaction discovered around 1950 by Boris Pavlovich Belousov. Solution of citric acid in water with acidified bromate and ceric ions oscillated from colorless to yellow for up to an hour. However, Belousov’s work ill-received by scientific community. Anatol Zhabotinsky then continued his work in 1961. Zhabotinsky succeeded in awakening the scientific community to the validity of chemical oscillators. The cerium-bromate reaction became known as the Belousov-Zhabotinsky (BZ) Reaction. Today, many chemical systems are known to oscillate and various mathematical models have been developed to describe the BZ reaction such as a Brusselator model and Oregonator model. To date, however, the actual reaction mechanism remains a mystery. The reaction mechanism to be studied, commonly called the Brusselator, is an example of an autocatalytic, oscillating chemical reaction. An autocatalytic reaction is one in which a species acts to increase the rate of its producing reaction. The vast majority of chemical reactions proceed to equilibrium through a monotonic mechanism. In recent years, however, nonlinear, oscillating chemical reactions have been widely studied, characterized, and modeled. Such chemical reactions share remarkable similarities with biological and neuronal processing that are capable of timing, switching, and signal propagation (Strizhak and Menzinger, 1996). Related reactions such as the Brusselator and the Belousov-Zhabotinsky reaction both display similar behavior and can be modeled
with related differential equations. The oscillatory nature of these reactions can be described by a stable limit cycle. The oscillatory behavior of these nonlinear systems was the topic of much debate in early years, as classical chemists argued that they violated the second law of thermodynamics (the Gibbs Free Energy of a system must decrease monotonically in a spontaneous process) (Pojman, Craven, and Leard, 1994). The spontaneous organization and the periodic changes in concentration of both reactants and products, however, can occur as long as the net entropy change in the universe is positive. Thus explaining why the concentrations of the intermediates can oscillate with time, while the free energy montonically decreases. The oscillatory nature of these reactions was experimentally observed as shown below. “The Brusselator” is an oscillating chemical reaction that was first described by Ilya Prigogine, a Belgian-American physical chemist. Generally, a reaction rate for a Smith 1 given reaction is proportional to the concentration of the reactants. For the generic reaction A + B C + D (1) the reaction rate, which is the change in concentration of the reactants, can be written as a function of the rate constant, k , and the concentrations of the reactants, written as [A] (Ault and Holmgreen, 2003). r = k [A] [B] (2) With the addition of a second chemical reaction, the system becomes nonlinear and thus more complex. 2 A 3 E (3) Since the coefficients of the reagents are now greater than one, the reaction rate of A can
Equilibria points for the system of differential equations given in (11) can be calculated by solving the system of equations below. a – bx – x + x 2 y = 0 (12) bx - x 2 y = 0