Belousov-Zhabotinsky reaction

Belousov-Zhabotinsky reaction

A Belousov-Zhabotinsky reaction, or BZ reaction, is one of a class of reactions that serve as a classical example of non-equilibrium thermodynamics, resulting in the establishment of a nonlinear chemical oscillator. The only common element in these oscillating systems are the inclusion of bromine and an acid. The reactions are theoretically important in that they show that chemical reactions do not have to be dominated by equilibrium thermodynamic behavior. These reactions are far from equilibrium and remain so for a significant length of time. In this sense, they provide an interesting chemical model of nonequilibrium biological phenomena, and the mathematical model of the BZ reactions themselves are of theoretical interest.

An essential aspect of the BZ reaction is its so called "excitability"- under the influence of stimuli, patterns develop in what would otherwise be a perfectly quiescent medium. Some clock reactions such as Briggs-Rauscher and BZ using the chemical ruthenium bipyridyl as catalyst can be excited into self-organising activity through the influence of light.

The discovery of the phenomenon is credited to Boris Belousov. He noted, sometime in the 1950s (the dates change depending on source, but it ranges from 1951 to 1958), that in a mix of potassium bromate, cerium(IV) sulfate, propanedioic acid and citric acid in dilute sulfuric acid, the ratio of concentration of the cerium(IV) and cerium(III) ions oscillated, causing the colour of the solution to oscillate between a yellow solution and a colorless solution. This is due to the cerium(IV) ions being reduced by propanedioic acid to cerium(III) ions, which are then oxidized back to cerium(IV) ions by bromate(V) ions.

Belousov made two attempts to publish his finding, but was rejected on the grounds that he could not explain his results to the satisfaction of the editors of the journals to which he submitted his results. His work was finally published in a less respectable, non-reviewed journal. [B. P. Belousov. Периодически действующая реакция и ее механизм. [A periodic reaction and its mechanism] . Сборник рефератов по радиационной медицине (Compilation of Abstracts on Radiation Medicine), 147:145, 1959.]

Later, in 1961, a graduate student named A. M. Zhabotinsky rediscovered this reaction sequence; [A. M. Zhabotinsky. Периодический процесс окисления малоновой кислоты растворе (исследование кинетики реакции Белоусова). [Periodic processes of malonic acid oxidation in a liquid phase.] Биофизика [Biofizika] , 9:306–311, 1964.] however, the results of these men's work were still not widely disseminated, and was not known in the West until a conference in Prague in 1968.

There are a number of BZ cocktails available in the chemical literature and on the web. Ferroin, a complex of phenanthroline and iron is a common indicator. These reactions, if carried out in petri dishes, result in the formation first of colored spots. These spots grow into a series of expanding concentric rings or perhaps expanding spirals similar to the patterns generated by a cyclic cellular automaton. The colors disappear if the dishes are shaken, and then reappear. The waves continue until the reagents are consumed. The reaction can also be performed in a beaker using a magnetic stirrer.

Andrew Adamatzky, a computer scientist in the University of the West of England reported on liquid logic gates using the BZ reaction. [Motoike I., Adamatzky A. Three-valued logic gates in reaction-diffusion excitable media. Chaos, Solitons & Fractals 24 (2005) 107-114. [http://uncomp.uwe.ac.uk/adamatzky] ]

ee also

* Excitable medium
* Briggs-Rauscher reaction

References


* Pabian and Zarins, "Banded Agates; Origins and inclusions", University of Nebraska-Lincoln, Educational circular #12.

External links

* [http://www.scholarpedia.org/article/Belousov-Zhabotinsky_reaction The Scholarpedia article on the Belousov-Zhabotinsky reaction]
* [http://staff.science.nus.edu.sg/~parwani/c1/node65.html The Belousov-Zhabotinski Reaction]
* [http://www.chem.leeds.ac.uk/chaos/pic_gal.html Gallery of BZ demonstrations]
* [http://online.redwoods.cc.ca.us/instruct/darnold/deproj/Sp98/Gabe/ The Belousov-Zhabotinsky Reaction]
* [http://www.ux.his.no/~ruoff/BZ_Phenomenology.html The Phenomenology of the Belousov-Zhabotinsky Reacton, with pictures]
* [http://youtube.com/watch?v=g3JbDybzYqk&feature=related Video of BZ reaction]
* [http://ed.augie.edu/~awaspaas/inorg/bz.pdf The Belousov-Zhabotinski Reaction] PDF file
* [http://technology.newscientist.com/channel/tech/dn13341-paper-cargo-surfs-chemical-waves.html?feedId=online-news_rss20 Paper cargo surfs chemical waves] - Oscillating chemical waves induced by BZ reactions can propel small objects, "New Scientist", 18 February 2008
* [http://hopf.chem.brandeis.edu/anatol.htm The home page of Anatol M. Zhabotinsky]


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • Belousov-Zhabotinsky reaction — BZR in einem gerührten System mit Ferroin BZR in einer dünnen Schicht, eine Wellenfront ist gelb markiert …   Deutsch Wikipedia

  • Belousov-Zhabotinsky-Reaktion — BZR in einem gerührten System mit Ferroin BZR in einer dünnen Schicht, eine Wellenfront ist gelb markiert …   Deutsch Wikipedia

  • Reactions Belousov-Zhabotinsky — Réactions Belousov Zhabotinsky C est le chimiste russe Belousov en 1950 qui découvrit la première réaction dite oscillante . En mélangeant cinq composés courants dans l eau, à température ambiante, on n atteint pas directement l état d… …   Wikipédia en Français

  • Réactions belousov-zhabotinsky — C est le chimiste russe Belousov en 1950 qui découvrit la première réaction dite oscillante . En mélangeant cinq composés courants dans l eau, à température ambiante, on n atteint pas directement l état d équilibre ; la solution oscille… …   Wikipédia en Français

  • Belousov — is a common Russian surname formed from the nickname Belye Usy ( ru. Белые Усы) meaning White Moustache which actually translates into English as Grey Moustache . To an intelligent Russian ear, the meaning is that of someone older, grey haired, i …   Wikipedia

  • Reaction–diffusion system — Reaction–diffusion systems are mathematical models which explain how the concentration of one or more substances distributed in space changes under the influence of two processes: local chemical reactions in which the substances are transformed… …   Wikipedia

  • Réactions Belousov-Zhabotinsky — C est le chimiste russe Belousov en 1950 qui découvrit la première réaction dite « oscillante ». En mélangeant cinq composés courants dans l eau, à température ambiante, on n atteint pas directement l état d équilibre ; la solution …   Wikipédia en Français

  • Réaction oscillante — Une réaction oscillante est un mélange complexe de composés chimiques dont la concentration d un ou plusieurs composants présente des changements périodiques. Dans les cas où l un des réactifs a une couleur visible, la traversée d un seuil de… …   Wikipédia en Français

  • Boris Pavlovich Belousov — (1893 1970) was a Soviet chemist / biophysicist who discovered the Belousov Zhabotinsky reaction (BZ reaction) in the early 50s. His work initiated the field of modern nonlinear chemical dynamics. [citebook|title=Handbook on the Physics and… …   Wikipedia

  • Briggs-Rauscher reaction — The Briggs Rauscher Oscillating Reaction is one of a small number of known oscillating chemical reactions. It is especially well suited for demonstration purposes because of its visually striking color changes: the freshly prepared colorless… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”