Periodicity and Chaos in Chemiluminescence: The Ruthenium-Catalyzed Belousov−Zhabotinsky Reaction

Chirality observed in a driven ruthenium-catalyzed Belousov-Zhabotinsky reaction model

Chirality is commonly associated with the spatial geometry of the atoms composing molecules, the biochemistry of living organisms, and spin properties. In sharp contrast, here we report chirality found in numerically computed stability diagrams of a chemical reaction governed by purely classical (that is, not quantum) equations, namely in a photochemically periodically perturbed ruthenium-catalyzed Belousov-Zhabotinsky reaction model. This novel chirality offers opportunities to explore hitherto unsuspected properties of purely classical chemical oscillators.

Mechanism and Phenomenology of an Oscillating Chemical Reaction

Chemical reactions, which are far from equilibrium, are capable of displaying oscillations in species concentrations and hence in colour, electrode potential, pH and/or temperature. The oscillations arise from the interplay between positive and negative kinetic feedback. Mechanisms for such reactions are presented, along with the rich phenomenology that these systems exhibit, from complex oscillations and chemical waves, to stationary concentration patterns. This review will focus on the Belousov-Zhabotinksy reaction but reference to other reactions will be made where appropriate.

The Tris(2,2'-Bipyridyl)Ruthenium-Catalysed Belousov–Zhabotinsky Reaction

The Belousov – Zhabotinsky (BZ) reaction is the prototypical oscillating chemical reaction. The tris(2,2'-bipyridine)ruthenium-catalysed BZ reaction (often simply referred to as the ruthenium-catalysed BZ reaction) displays photosensitivity and has been widely exploited for examination of the effects of illumination on nonlinear reaction kinetics. In this review, we investigate the behaviour of the ruthenium-catalysed BZ reaction. The mechanism of the reaction is analysed and we examine how light sensitivity is incorporated into kinetic models of the reaction. The temporal dynamics of the photosensitive reaction is presented and, finally, we discuss the extraordinary wealth of behaviour that has been observed in the spatially-distributed system when perturbed by visible light.

Long-Lasting Complex Reaction Behavior in a Closed Ferroin-Bromate-Hydroxybenzenesulfonate System

The bromate-phenolsulfonate reaction was found to exhibit spontaneous oscillations in a batch reactor, where the addition of small amounts of ferroin would result in nonoscillatory behavior. As the ferroin concentration was increased, the system produced very rich nonlinear behavior, including three isolated oscillatory regimes that were separated by as long as 48 h nonoscillatory period. The long-lasting nonlinear behavior may be attributed to the slow desulfonation of phenolsulfonate in an acidic solution, forming phenol-like intermediates. However, unlike the bromate-phenol oscillator, oxygen was found to greatly influence the reaction, and various complex oscillations could be observed by tuning the oxygen concentration. Mechanistic studies performed through employing ¹H NMR spectroscopy and mass spectrometry to measure intermediate species at different stages of the reaction were able to identify 1,4-benzoquinone, 2-bromo-1,4-benzoquinone, 2,6-dibromo-1,4-benzoquinone, and 2,4,6-tribromophenol as major components during the reaction.

Complex oscillations in a simple model for the Briggs-Rauscher reaction

Complex oscillations in a simple model of the Briggs-Rauscher reaction mechanism in a continuously stirred tank reactor proposed by Kim et al. [J. Chem. Phys. 117, 2710 (2002)] are investigated numerically. The k(0)-[CH(2)(COOH)(2)](0) phase diagram is constructed first where k(0) is the flow rate and [...](0) is the input concentration. Within the region surrounded by the Hopf bifurcation curve, we find complex oscillation regions which are again separated from the regular oscillation region by the secondary Hopf bifurcation curves. Mixed mode oscillations with an incomplete Farey sequence, periodic-chaotic (or nonperiodic) sequence, and various types of burst oscillations are observed in complex oscillation regions. Also, chaotic burst oscillations, which are due to the transition from one kind of burst to another kind, are reported.

Periodic and Bursting pH Oscillations in an Enzyme Model Reaction

Oscillatory behaviour in the pH value was observed during the oxidation of sulfite by hydrogen peroxide mediated by hemin in a continuous-flow stirred tank reactor. The dynamics of this reaction was studied for a variety of flow rates of the reactants. As the flow rates increase, the oscillations evolve from relaxation oscillations to more complex shapes, displaying, among others, bursting behaviour. A reaction mechanism is proposed that involves the autocatalytic oxidation of HSO