The 1,4-cyclohexanedione-bromate-acid oscillatory system I. Its organic chemistry

Kurin-Csörgei, Krisztina; Szalai, István; Molnár-Perl, I.; Kőrös, E.

doi:10.1007/bf02070120

Cited by 28 publications

(23 citation statements)

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“…They used ferroin at a concentration of 5 × 10 -4 M and considered it to be only an indicator, implying that the reaction is an uncatalyzed bromate oscillator (UBO). [9][10][11][12] Here we present further results related to both the uncatalyzed and the ferroin-catalyzed systems. We study the dependence of the system dynamics on the initial reagent concentrations, with that of ferroin varied from 0 to 5 × 10 -3 M, and show that the system behaves like a typical BZ oscillator if the concentration of ferroin exceeds 5 × 10 -5 M.…”

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Bromate−1,4-Cyclohexanedione−Ferroin Gas-Free Oscillating Reaction. 1. Basic Features and Crossing Wave Patterns in a Reaction−Diffusion System without Gel

et al. 1996

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We present a study of the bromate-1,4-cyclohexanedione-ferroin oscillating reaction in both well-stirred and reaction-diffusion systems. We investigate the dependence of the system dynamics on the initial reagent concentrations, with the initial concentration of ferroin varied from 0 to 5 × 10 -3 M, and show that the system behaves like a typical BZ oscillator if the concentration of ferroin exceeds 5 × 10 -5 M. We demonstrate spontaneous formation of spiral waves and transverse wave fronts in quasi-two-dimensional systems and formation of crossing wave patterns in thin layers of solution open to air. IntroductionThe Belousov-Zhabotinsky (BZ) reaction-diffusion system is perhaps the most commonly employed tool for experiments on chemical waves and pattern formation. [1][2][3][4][5][6][7] The ferroincatalyzed reaction with malonic acid as the initial reductant has been the most frequently used BZ system for this purpose. An important drawback of this reaction is the production of carbon dioxide, which results in the formation of bubbles that disturb the reaction-diffusion patterns and make it difficult to conduct lengthy experiments in either batch or open reactors. Attempts have been made to develop gas-free versions of the BZ reaction. 8 Unfortunately, these variants do not generate the range of chemical wave behavior found in the ferroin-malonic acid BZ reaction. Recently, showed that target patterns develop in the bromate-1,4-cyclohexanedione-ferroin reaction-diffusion system without formation of bubbles. They used ferroin at a concentration of 5 × 10 -4 M and considered it to be only an indicator, implying that the reaction is an uncatalyzed bromate oscillator (UBO). [9][10][11][12] Here we present further results related to both the uncatalyzed and the ferroin-catalyzed systems. We study the dependence of the system dynamics on the initial reagent concentrations, with that of ferroin varied from 0 to 5 × 10 -3 M, and show that the system behaves like a typical BZ oscillator if the concentration of ferroin exceeds 5 × 10 -5 M.The absence of bubbles and precipitate makes the present system an excellent tool for experiments on chemical waves and patterns. We demonstrate spontaneous formation of spiral waves and transverse wave fronts in quasi-two-dimensional systems and the formation of crossing wave patterns in thin layers of solution open to air.Some preliminary mechanistic considerations are also suggested. Experimental SectionMaterials. Stock solutions of 1.0 M NaBrO 3 (Janssen Chimica, 99+%), 0.3 M 1,4-cyclohexanedione (abbreviated as CHD) (Aldrich, 98%) dissolved in 1.0 M H 2 SO 4 by stirring the solution on a hot plate (40-50°C) for about 30 min, 0.025 M ferroin (prepared from the calculated amount of FeSO 4 ‚7H 2 O (Fisher, certified) and 1,10-phenanthroline (Aldrich, 99+%)), 0.2 M NaBr (Fisher, certified), and 1.0-10.0 M H 2 SO 4 were used to prepare the working solutions.Apparatus and Procedures. Batch experiments with the bromate-CHD and the bromate-CHD-ferroin systems were performed in a thermosta...

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Bromate−1,4-Cyclohexanedione−Ferroin Gas-Free Oscillating Reaction. 1. Basic Features and Crossing Wave Patterns in a Reaction−Diffusion System without Gel

et al. 1996

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“…Notice that the reaction products of CHD do not involve any gaseous compounds and, hence, no detrimental gas bubbles are formed during the experiment. 26 In all experiments, the concentrations of the catalyst and sulfuric acid are 0.5 and 90 mM, respectively. Notice that, after the preparation of the reaction solution, the system remains homogeneously oxidized for up to 6 h. Quasi-two-dimensional reaction conditions are created between two circular polystyrene plates with a diameter of 10 cm.…”

Section: Methodsmentioning

confidence: 99%

Meandering Spiral Waves in the 1,4-Cyclohexanedione Belousov−Zhabotinsky System Catalyzed by Fe[batho(SO₃)₂]₃^4-/3-

2003

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Meandering spiral waves are observed in the 1,4-cyclohexanedione Belousov-Zhabotinsky (CHD-BZ) reaction at very low concentrations (3-35 mM) of the organic substrate. The spiral tips describe hypocycle-like trajectories indicating the presence of two main rotation periods and radii. The ratio of these periods approaches 1 for decreasing concentrations of CHD. In this limit, we find Z-shaped trajectories with approximately two lobes. The use of Fe[batho(SO 3 ) 2 ] 3 4-/3-as the BZ catalyst gives rise to extremely long rotation periods (1000-4000 s), and the tip trajectories span large areas of up to 40 mm 2 . As a result of the absence of gaseous products and the high absorption of the catalyst, this particular system is ideally suited for the investigation of spiral waves in closed, thin-layer systems, such as nonuniformly curved and micropatterned media.

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“…9 A maioria dos UBOs utiliza em sua composição compostos aromáticos (principalmente derivados do fenol ou da anilina) como substrato orgânico e o íon bromato em meio ácido (geralmente ácido sulfúrico). 10 Farage e Janjic 11,12 descobriram que a 1,4-ciclo-hexanodiona (uma dicetona alicíclica) reage com o bromato em meio ácido apresentando um comportamento oscilatório. A originalidade dessa descoberta reside não apenas no fato de que o sistema oscila sem catalisador, mas no fato do fenômeno oscilatório ocorrer também em soluções de ácido sulfúrico (H 2 SO 4 ), ácido nítrico (HNO 3 ), ácido perclórico (HClO 4 ) e ácido fosfórico (H 3 PO 4 ).…”

Section: Introductionunclassified

“…11,12 Sabe-se que a primeira etapa da oxidação da 1,4-CHD pelo íon bromato é a abstração de um hidrogênio (processo de aromatização), em lugar da quebra da cadeia orgânica que poderia resultar, por exemplo, na formação do dióxido de carbono (CO 2 ). 10 Nestes estudos, verificou-se que o composto majoritário encontrado é o 1,4-di-hidroxibenzeno (H 2 Q) mais conhecido como hidroquinona, que é posteriormente oxidado a 1,4-benzoquinona (Q), sendo este um dos principais produtos da reação. A reação de bromação, que está sempre acompanhada da oxidação quando o íon bromato é o oxidante, tem como principais produtos, mono-e dibromo-derivados da 1,4-CHD e 1,4-bromobenzoquinona.…”

Section: Introductionunclassified

Dinâmica oscilatória em sistemas contendo bromato e 1,4-ciclo-hexanodiona em meio ácido: I. Efeito da temperatura

Oliveira¹,

Oliveira²,

Varela³

2012

Quím. Nova

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Recebido em 16/5/11; aceito em 11/8/11; publicado na web em 30/9/11 OSCILLATORY DYNAMICS IN SYSTEMS CONTAINING BROMATE AND 1,4-CYCLOHEXANEDIONE IN ACIDIC MEDIA. I. THE EFFECT OF TEMPERATURE. We present in this work the influence of temperature on the dynamics of homogeneous chemical systems containing bromate and 1,4-cyclohexanedione (1,4-CHD) in acidic media. In particular, the following systems were studied: bromate/1,4-CHD/acid, bromate/1,4-CHD/ferroin/acid and bromate/1,4-CHD/trisbipyridine ruthenium/acid. Investigations were carried out by means of an electrochemical probe, at five temperatures between 5 and 45 °C. Activation energies (E a ) were estimated in different ways for the pre-oscillatory and oscillatory regimes. In any case, the E a was found to depend on the catalyst, composition and initial concentrations. In addition, it was observed that ferroin and trisbipyridine ruthenium act as catalysts only during the transition between the induction period and oscillatory regime.Keywords: oscillations; complex kinetics; 1,4-cyclohexanedione. INTRODUÇÃOUma das principais características dos sistemas vivos é a presença de ritmos nas funções regulatórias, exemplos incluem processos em diferentes níveis como os ritmos circadianos, batimentos cardíacos, ciclo menstrual, ciclo de Krebs e outros ciclos intracelulares, como a glicólise. Fenômenos desta natureza são normalmente referidos como processos de auto-organização temporal e também ocorrem em várias reações químicas na forma de oscilações nas concentrações de espécies intermediárias. Em sistemas abertos, o regime oscilatório pode persistir indefinidamente, desde que a alimentação de reagentes frescos e a remoção de produtos formados ocorram de forma adequada. Em sistemas fechados, por outro lado, as oscilações ocorrem de forma transiente e cessam quando a diminuição dos reagentes move o sistema para fora da bacia de atração referente ao estado oscilatório. Adicionalmente aos processos auto-organizados em domínio temporal, o transporte de espécies, fundamentalmente via difusão, pode cooperar com as etapas químicas envolvidas e em determinadas circunstâncias levar à formação de estruturas espaço-temporais. 1 A auto-organização dinâmica ocorre em diversos sistemas físico-químicos abertos e afastados do estado de equilíbrio e vem se tornando uma área de intensa pesquisa. 2 Indubitavelmente, os osciladores homogêneos baseados na redução de bromato são os mais estudados. 3 A origem destes osciladores se deu na Rússia, em 1951, quando Boris Pavlovich Belousov, interessado no ciclo de Krebs, estudava a reação entre bromato e ácido cítrico em meio ácido com íons cério Ce(IV). Belousov esperava observar uma mudança na coloração da solução de amarelo para incolor, como resultado da redução do Ce(IV) para Ce(III). Em lugar de uma simples transição, a solução mudou de cor do amarelo para o incolor por diversas vezes. Belousov só conseguiu publicar sua descoberta em 1958, em um periódico bem pouco conhecido. Em 1961, Anatol M. Zhabotinskii deu continuidade ao trabalho ...

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The 1,4-cyclohexanedione-bromate-acid oscillatory system I. Its organic chemistry

Cited by 28 publications

References 11 publications

Bromate−1,4-Cyclohexanedione−Ferroin Gas-Free Oscillating Reaction. 1. Basic Features and Crossing Wave Patterns in a Reaction−Diffusion System without Gel

Bromate−1,4-Cyclohexanedione−Ferroin Gas-Free Oscillating Reaction. 1. Basic Features and Crossing Wave Patterns in a Reaction−Diffusion System without Gel

Meandering Spiral Waves in the 1,4-Cyclohexanedione Belousov−Zhabotinsky System Catalyzed by Fe[batho(SO₃)₂]₃^4-/3-

Dinâmica oscilatória em sistemas contendo bromato e 1,4-ciclo-hexanodiona em meio ácido: I. Efeito da temperatura

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The 1,4-cyclohexanedione-bromate-acid oscillatory system I. Its organic chemistry

Cited by 28 publications

References 11 publications

Bromate−1,4-Cyclohexanedione−Ferroin Gas-Free Oscillating Reaction. 1. Basic Features and Crossing Wave Patterns in a Reaction−Diffusion System without Gel

Bromate−1,4-Cyclohexanedione−Ferroin Gas-Free Oscillating Reaction. 1. Basic Features and Crossing Wave Patterns in a Reaction−Diffusion System without Gel

Meandering Spiral Waves in the 1,4-Cyclohexanedione Belousov−Zhabotinsky System Catalyzed by Fe[batho(SO3)2]34-/3-

Dinâmica oscilatória em sistemas contendo bromato e 1,4-ciclo-hexanodiona em meio ácido: I. Efeito da temperatura

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Meandering Spiral Waves in the 1,4-Cyclohexanedione Belousov−Zhabotinsky System Catalyzed by Fe[batho(SO₃)₂]₃^4-/3-