Complex chemical reactions — A review

Abstract

Complex responses have been observed in a wide range of chemical and engineering systems: In well-stirred and unstirred solution-phase, in gels, in heterogeneous catalysis and dissolution reactions, in gas-and solid-phase combustion, widely in biological systems, accompanying phase transitions, in atmospheric kinetics and even in interstellar dust clouds. Complex behaviour does not, however, imply a necessarily complex underlying chemical mechanism. The appropriate feedback mechanisms, built on chainbranching, autocatalysis or self-heating, arise quite commonly in Nature. In many instances, it is appropriate "rst to attempt to "nd reduced mechanisms giving a semi-quantitative "t to observed responses. An example of such an approach applied to a model for complex oscillations of species concentrations in the mesosphere is presented, and the reduced model used to investigate the e!ects of longitudinal mixing in this system. Once a general understanding of a particular reaction system has been obtained, more detailed questions can be addressed. This is exempli"ed by a study of the development of three-dimensional scroll waves in the Belousov}Zhabotinsky reaction. Such detailed information for a speci"c reaction also informs the general understanding of the class of &excitable media'.

Periodic Travelling Wave Selection by Dirichlet Boundary Conditions in Oscillatory Reaction-Diffusion Systems

“…Periodic travelling waves (PTWs) are a fundamental solution form in oscillatory reaction-diffusion equations, by which I mean reaction-diffusion systems whose kinetics have a stable limit cycle. PTWs are the one-dimensional analogue of spiral waves and target patterns, and underlie many observed behaviors in biology and chemistry (Bjørnstad, Ims, and Lambin (1999); Scott et al (2000)). In 1973, Kopell and Howard published their seminal paper, which showed that a reaction-diffusion system develops a one-parameter family of PTWs as its kinetics pass through a Hopf bifurcation.…”

Reactive-diffusion waves in the mesospheric photochemical system

“…We do not model the very high latitude region. As follows from Johnson et al (1998) and Scott et al (2000), two-day oscillations in this region are suppressed for real values of horizontal eddy diffusion coefficient.…”

Mechanism and Phenomenology of an Oscillating Chemical Reaction

“…The concentrations of Br 2 and CO 2 oscillate without an induction period in this system, and it is necessary to bubble an inert gas such as N 2 through the reaction mixture in order to observe oscillations. This behaviour may be explained by including bromine hydrolysis, a rate of removal of Br 2 (24), and steps (25) and (26) to the FKN:…”

“…The scientific activity associated with this reaction is still strong, and it remains a useful way of testing nonlinear kinetic theory [23]. It is undoubtedly the most extensively studied oscillating chemical reaction [24][25][26][27]. This review will focus primarily on the BZ reaction; however, reference to other reactions will be made where appropriate.…”