Bray-Liebhafsky Reaction Research Articles

The Bray–Liebhafsky Oscillatory Reaction as a Chemosensor for Benzenediols

Benezediols are widely used in different areas of industry, thus identification and quantification of benzenediols is of utmost importance due to their toxicity and high environmental abundance. In this work, benzenediol isomers (pyrocatechol, resorcinol, and hydroquinone) were investigated by using the Bray–Liebhafsky (BL) oscillatory reaction. All three isomers exhibit different behavior in the BL reaction, which renders the BL system applicable as a chemosensor. The period between the fifth and sixth oscillation, the amplitude of the sixth oscillation and in the case of hydroquinone, the emergence of a new oscillation in the BL reaction were selected as the parameters used for the identification and quantification of these isomers. Furthermore, electron paramagnetic resonance spectroscopy and DFT calculations were performed in order to provide insights into the mechanism of benzenediols reactions with the BL system.

A mathematical model of the Bray–Liebhafsky reaction

It is known that the widely studied Bray–Liebhafsky reaction typically exhibits complex chemical behaviour. Numerous mathematical systems have been proposed to describe the iodine oscillations that occur during this process. Recently, a four-variable model of the Bray–Liebhafsky reaction has been proposed and analytical and numerical investigations suggested that chaotic solutions may exist. We revisit this four-variable model here and perform what appears to be the first detailed work on this system. We suggest that this model is perhaps not chaotic after all. Informed by these fresh insights, we propose a reduced two-variable model based upon the four-variable system. This model is created with the twin goals of enabling simpler mathematical analysis while retaining the underlying chemical mechanisms. We are able to demonstrate that our reduced problem performs very well when compared with the full model for realistic parameter values. In particular, key regions of parameter space are identified within which temporal oscillations can occur. Moreover, these persistent oscillations are consistent with the available qualitative experimental observations.

Influence of L-tyrosine on dynamics of Bray-Liebhafsky oscillatory reaction in batch reactor. Experimental investigation and numerical modeling

The impact of L-tyrosine on the dynamics of the Bray-Liebhafsky (BL) oscillatory reaction was investigated both experimentally and numerically. The study focused on the examination of the sensitivity of the BL reaction to L-tyrosine perturbation. The results obtained indicated possible pathways of influence. Simulations were carried out with and without L-tyrosine. The interaction of L-tyrosine with the BL reaction system was tested with two possible reactions.

Experimental support for the model of Bray–Liebhafsky oscillatory reaction based on the heterogeneous effects

Participation of the heterogeneous effects in the Bray–Liebhafsky reaction. Content of the large bubbles in the mixture under fast and slow stirring rate with corresponding effects on oscillatory dynamics.

Changing the paradigm in modelling the Bray-Liebhafsky oscillatory chemical reaction.

The Bray-Liebhafsky (BL) reaction is one of the simplest chemical oscillators consisting initially of only three components. Despite this, its mechanism is unknown for more than 100 years due to the absence of selective, sensitive, and fast experimental techniques for following all of the involved intermediates. The modeling of the BL mechanism assumes presumably mass action kinetics "adjustable" to oscillatory solutions by the application of mathematical stability analysis and treating the system as homogeneous. Such a basically mathematical approach need not suggest physically realistic kinetic parameters and is not unique since a number of models can be proposed. Based on recent experimental and computational results, a new model of the BL oscillatory reaction mechanism is constructed by including heterogeneous processes occurring in the system. The same set of equations is able to demonstrate not only the oscillatory evolution but also mixing effects on the oscillatory dynamics, and non-oscillatory stepwise-iodine oxidation and can rationalize other effects described in literature. Thus, the paradigm of treating the BL oscillatory system as a homogeneous one, described by formal kinetics only, is extended for a better understanding of the chemistry of this apparently simple system. The introduced ideas of energy redistribution may contribute to establishing an improved conceptual base for considering other complex oscillators in various fields of science.

Continuous measurements of gaseous oxygen production in Bray-Liebhafsky oscillatory reaction and its correlation with the reaction mechanism

• Experimental setup for evolved oxigen monitoring was constructed. • Bray-Liebhafsky reaction was investigated at 2 mixing rates in 5 replicates. • Lower mixing rate preserve higher content of dissolved gas. • Lower stirring facilitate oscillatory evolution. • Heterogeneous effects assist in triggering iodine oxidation. Upgraded design of the experimental setup for monitoring Bray-Liebhafsky (BL) oscillatory reaction dynamics allowed simultaneous recording of platinum electrode potential and gaseous pressure changes over time. Experiments were performed at two stirring rates (600 rpm and 1200 rpm) in five replicates. Evolved gas at two mixing rates is correlated with reaction induction period, number of oscillations, period between oscillations, oscillation amplitude and number of produced oxygen moles per oscillation. Obtained trends indicate that the amount of formed gas facilitates initiation of iodine oxidation. Results are in agreement with previous findings which point to the importance of heterogeneous effects in reaction of iodine oxidation.

Kinetics and mechanism of I(+ 3) reactions and consequences for other iodine reactions

This article presents new kinetic studies of the disproportionation of I(+ 3) and of its oxidation by H2O2. It also provides an update of the previously proposed model for reactions of iodine compounds with oxidation numbers from − 1 to + 5 with each other and with H2O2. This model explains the kinetics of several reactions, including the oxidation of iodine by H2O2. We show that the reduction of HOI by H2O2 results from \({\text{HOI }} + {\text{ H}}_{{2}} {\text{O}}_{{2}} \to {\text{HOOI }} + {\text{ H}}_{{2}} {\text{O}}\) followed by the reversible reaction \({\text{HOOI}} \rightleftharpoons {\text{I}}^{ - } + {\text{ H}}^{ + } + {\text{ O}}_{{2}}\). An analysis of previous measurements of the kinetic constant k(HOI + H2O2) explains the large differences between the values proposed in the literature and gives k(HOI + H2O2) = 6 M−1 s−1. The reversibility of the reaction \({\text{HOOI}} \rightleftharpoons {\text{I}}^{ - } + {\text{ H}}^{ + } + {\text{ O}}_{{2}}\) suggests a new explanation for the effect of oxygen on the Bray–Liebhafsky reaction. H2O2 would oxidize HOOI by a radical mechanism.

Intermittent Chaos in the CSTR Bray-Liebhafsky Oscillator-Specific Flow Rate Dependence.

Dynamic states with intermittent oscillations consist of a chaotic mixture of large amplitude relaxation oscillations grouped in bursts, and between them, small-amplitude sinusoidal oscillations, or even the quiescent parts, known as gaps. In this study, intermittent dynamic states were generated in Bray–Liebhafsky (BL) oscillatory reaction in an isothermal continuously-fed, well-stirred tank reactor (CSTR) controled by changes of specific flow rate. The intermittent states were found between two regular periodic states and obtained for specific flow rate values from 0.020 to 0.082 min−1. Phenomenological analysis based on the quantitative characteristics of intermittent oscillations, as well as, the largest Lyapunov exponents calculated from experimentally obtained time series, both indicated the same type of behavior. Namely, fully developed chaos arises when approaching to the vertical asymptote which is somewhere between two bifurcations. Hence, this study proposes described route to fully developed chaos in the Bray-Liebhafsky oscillatory reaction as an explanation for experimentally observed intermittent dynamics. This is in correlation with our previously obtained results where the most chaotic intermittent chaos was achieved between the periodic oscillatory dynamic state and stable steady state, generated in BL under CSTR conditions by varying temperature and inflow potassium iodate concentration. Moreover, it was shown that, besides the largest Lyapunov exponent, analysis of chaos in experimentally obtained intermittent states can be achieved by a simpler approach which involves using the quantitative characteristics of the BL reaction evolution, that is, the number and length of gaps and bursts obtained for the various values of specific flow rates.

Insight into the Origin of Pyrocatechol Inhibition on Oscillating Bray-Liebhafsky Reaction: Combined Experimental and Theoretical Study

Abstract The pyrocatechol inhibitory effect on the oscillatory Bray-Liebhafsky (BL) reaction is reported. Obtained results are compared with those available in the literature (R. Cervellati et al, Helvetica Chimica Acta 2001) for Briggs-Rauscher (BR) reaction with pyrocatechol addition. The two orders of magnitude larger calibration curve slope obtained in BR in comparison to BL reaction, suggests that different reactions are responsible for inhibitory effects in these systems. The potential explanation of pyrocatechol behavior is given by employing the ultraviolet-visible (UV/VIS) spectroscopy, density functional theory, and coupled cluster computational methods. The last two were employed for the first time to discover potential candidates among unstable chemical species HIO, HIO2, I2O, HOO•, HO•, IO•, IO2•, and I• of the BL (and BR) system for reaction with pyrocatechol. The calculated reaction rate constants for the hydrogen atom transfer reactions between pyrocatechol and free radical intermediates indicate the following order of reactivity: HO• > IO• > HOO• > IO2•. The same order of reactivity is also observed in the case of a thermodynamic investigation. In addition, kinetic insight indicates that the inhibitory behavior of pyrocatechol could not be explained with one particular chemical reaction in the BL (or in the BR) oscillatory system.

Bifurcation analysis: a tool for determining model parameters of the considered process

In this paper, we intend to show the importance of the bifurcation analysis in understanding of an oscillatory process. Hence, we use the bifurcation diagram of the Bray–Liebhafsky reaction performed in continuous well-stirred tank reactor under controlled temperature variations for the determination of the activation energies as well as rate constants of particular steps appearing in the kinetic model of oscillatory reaction mechanism. This approach has led us to the development of general procedure for treatment of experimentally obtained data and extracting kinetic parameters from them, which was very important considering that some rate constants of the already proposed model could not be determined experimentally and have to be fitted (or guessed). Also, the proposed approach has the potential to inspire the refinement of already proposed models and the development of a new one that will be able to reproduce experimentally obtained system’s dynamical features more successfully. In particular, the dynamic states of the Bray–Liebhafsky oscillatory reaction have been analyzed experimentally and numerically using already proposed model together with qualitative and quantitative analysis of bifurcation diagrams in both cases.

Reactions of iodate with iodine in concentrated sulfuric acid. Formation of I(+3) and I(+1) compounds

The absorption spectra in a large range of concentrations show that the reactions of iodate with iodine in 96% sulfuric acid produce (IO)HSO4, I3+ and I5+, just like in the pure 100% acid. We discovered that, in 96% H2SO4, these reactions also produce I2O which is not formed in the pure acid. I2O is an important intermediate of reactions in diluted sulfuric acid, including the Bray-Liebhafsky reaction, but it had never been observed directly because of its very high reactivity. The equilibrium constants of the reactions producing these four compounds were determined.

Erratum to: Bifurcation analysis of the reduced model of the Bray–Liebhafsky reaction

Erratum to: Bifurcation analysis of the reduced model of the Bray–Liebhafsky reaction

Bifurcation analysis of the reduced model of the Bray–Liebhafsky reaction

In this paper, an already published model of the Bray–Liebhafsky reaction was improved by removing the direct autoinhibitory step, which resulted in a new variant of the model with more realistic kinetic scheme than the earlier version. The obtained variant of the model retains all intermediate species (I−, HIO, HIO2 and I2) that were present in the previous model and has one reaction less. Stability analysis of the improved model was performed by stoichiometric network analysis (SNA). By this method, it was shown that improved model can simulate Andronov–Hopf and saddle-node bifurcations. In order to confirm the results of SNA, bifurcation analysis was performed with the initial concentrations of [H2O2]0 as the control parameter. With selected set of rate constants and constant concentrations of external species, two Andronov–Hopf bifurcations were detected at [H2O2]0 = 5.62 × 10−2 M and [H2O2]0 = 10.73 M, while the rate constants ought to be changed for a saddle-node to occur. Bifurcation analysis also showed that the interaction between intermediate species I–, HIO and HIO2 has a crucial impact on the emergence of Andronov–Hopf bifurcation.

Return map analysis of the highly nonlinear Bray–Liebhafsky reaction model

By numerically simulated Bray–Liebhafsky (BL) reaction under a continuously fed well stirred tank reactor (CSTR) conditions, we discussed the attractors and Poincare 1D maps with respect to flow rate as the control parameter. The new technique of the return maps from transient trajectories over the slow manifold is developed and applied in order to explore its multilayered structure related to dynamical states (periodic and aperiodic -chaotic oscillating modes) of the system. Kinetic relations underlying the slow manifold structure are briefly discussed.

Dynamic transitions in the Bray–Liebhafsky oscillating reaction. Effect of hydrogen peroxide and temperature on bifurcation

The temporal dynamics of the Bray–Liebhafsky reaction (iodate-based catalytic decomposition of hydrogen peroxide in an acidic aqueous solution) was experimentally characterized in a continuous stirred tank reactor by independently varying the temperature and the mixed inflow hydrogen peroxide concentration. When the temperature was the bifurcation parameter, the emergence/disappearance of oscillatory behavior via a supercritical Andronov–Hopf bifurcation was observed for different mixed inflow hydrogen peroxide concentrations. An increase in the mixed inflow hydrogen-peroxide concentration resulted in a shift of the bifurcation point towards higher values of temperature, but did not alter the bifurcation type.

Bray–Liebhafsky and non-catalysed Briggs–Rauscher oscillating reactions

In order to propose mechanisms of complicated chemical systems, it is necessary to study simpler subsystems. The mechanism we have proposed for the Bray–Liebhafsky (BL) oscillating reaction is based on kinetic studies of several reactions of iodine compounds between them and with hydrogen peroxide. Because the reactants of the non-catalysed Briggs–Rauscher (BR) oscillating reaction are the same as those of the BL reaction plus malonic acid, we propose now to extend the mechanism of the BL reaction to the BR reaction. With this aim, we add radical reactions of iodine compounds and of malonic acid. The choice of these reactions is based on our recent study of the unusual kinetics of the iodate reduction by high concentrations of hydrogen peroxide.

Bray–Liebhafsky oscillatory reaction in the radiofrequency electromagnetic field

Oscillatory Bray–Liebhafsky (BL) reaction is capacitively coupled with the electromagnetic radiation in the frequency range 60–110MHz. Because of the specific reaction dynamics characterized by several characteristic parameters (induction period, period between chemical oscillations and their amplitude) it served as a good model system for the investigation of the effects of radiofrequent (RF) radiation. RF power of up to 0.2W did not produce observable changes of the BL reaction parameters in the limit of the experiment reproductivity. Results indicate that, under the given experimental conditions, both dissipative and reactive properties of the solution are not considerably coupled with the RF electrical field.

Influence of Chemically Inert Cations on the Hydrogen-bond Network in the Bray-Liebhafsky Oscillatory Reaction

The influence of the chemically inert alkali metal cations on the Bray-Liebhafsky oscillatory reaction dynamics was investigated by the addition of the same amount of various sulfates to the reaction mixture. Beside the expected changes related to the altered acidity of the sulfuric acid solution, subtle changes dependent on cation dimensions were noticed. Larger cations have more impact on the Bray-Liebhafsky reaction dynamics. Analysing the mean ionic activity of salts, it is suggested that the effects may be related to the altered extent of water hydrogen bonding and specific role of bulk water in the reaction mechanism.

Reexamination of Gas Production in the Bray–Liebhafsky Reaction: What Happened to O2 Pulses?

Results of high-precision measurements of gas production in the BL reaction are presented, and an efficient kinetic model for their analysis is proposed. Based on this model, the data have been examined pulse by pulse, and for the first time, the entire records of gas production could be successfully reduced to series of just a few key parameters. It has been confirmed that the kinetics of O2(g) production is of the first order with respect to its precursor. Overall, only two steps have been found necessary to fit the observed pulses in gas production. The first step produces the precursor of the recorded O2(g), and its rate has two components. One component provides the peaks, and its approximation in the form of Gaussian functions has been found as satisfactory. The other component provides the constant baseline of gas production between the pulses. Finally, the precursor gives rise to O2(g) in the second step, and the simple first-order kinetics suggests that the precursor is otherwise relatively unreactive, making O2(aq) a logical candidate. However, the rate constant of this process showed almost perfect linearity with the actual concentrations of H2O2, and it was affected only little by variations in the rate of stirring. It thus seems possible that this final step in gas production, responsible for the majority of O2 produced in pulses, might not be the interphase transport O2(aq) → O2(g), as expected. Instead, it might be a truly chemical process, giving rise to O2(g) in a reaction of H2O2 with another precursor, which is not involved significantly in any other process, but it is not O2(aq). If this is true, the second-order rate constant of this process in the system with initial composition of 0.360 M KIO3, 0.345 M H2O2, and 0.055 M HClO4 at 60 °C would be 0.25-0.30 M(-1)·s(-1), depending on the rate of stirring.

Radicals in the Bray–Liebhafsky Oscillatory Reaction

This study investigates the formation of free radicals in the Bray-Liebhafsky (BL) oscillatory reaction. The results indicate that radicals are produced during both monotonous and oscillatory dynamics observed as the change of the electron paramagnetic signal (EPR) of the spin-probe TEMPONE. EPR spin-trapping with DEPMPO suggested that the most abundant radical produced in the BL reaction is an iodine-centered radical. The EPR spectrum of the DEPMPO/iodine-centered radical adducts has not been previously reported. This study may aid in establishing a more realistic reaction mechanism of the BL reaction and related chemical oscillators.