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Articles dans des revues avec comité de lecture

2022

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 HOI+H2O2→HOOI+H2O followed by the reversible reaction HOOI⇌I-+H++O2. 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 HOOI⇌I-+H++O2 suggests a new explanation for the effect of oxygen on the Bray-Liebhafsky reaction. H2O2 would oxidize HOOI by a radical mechanism.

Bray-Liebhafsky oscillations at room temperature

Concentration ranges where Bray-Liebhafsky oscillations appear at room temperature have been explored. The periods are very long and the maxima of the iodine concentration little reproducible, most likely due to the effect of the oxygen produced by the reaction. The experimental results are compared to numerical simulations made with the model published in the same issue of this journal.

2019

Fundamental concepts in chemical kinetics

Students and young researchers will find in this article a clear and accurate presentation of fundamental concepts in chemical kinetics: reaction rates, elementary reactions and mechanisms, kinetic constants and relation to thermodynamics, and energies of activation. The discussions are based on specialized literature without going into detail and avoid misunderstandings and sometimes errors found in the general literature and on the Internet. With this aim, an original approach is sometimes adopted.

I2O in solution and volatility

I(+1) formed by reacting iodine with KIO3 in 96% sulfuric acid is partly in the form of I2O that can be extracted in dichloromethane (DCM). The extraction process is an interesting coupling between phase transfer and chemical reactions allowing to obtain solutions containing nearly no iodine. I2O solutions can also be obtained in other chlorinated solvents and forms probably an ionic complex in acetonitrile. UV-vis spectra are presented (ε (I2O, 442 nm) = 259 in DCM). Distillations of I2O solutions and gas phase diffusion at laboratory temperature show that I2O is a volatile compound that should be considered in atmospheric chemistry.

2018

Effects of Ce(III) and Mn(II) on the Dushman reaction and simulations of the Briggs-Rausher reaction

The Dushman reaction (reduction of iodate by iodide) is a subsystem of the Briggs-Rausher oscillating reaction. We show that the previously observed effects of Ce(III) and Mn(II) on the kinetics of the Dushman reaction are mainly ionic strength effects. The observed decrease of the rate constant of the Dushman reaction when the ionic strength increases and the formation of the ion pairs MnSO4(aq) and CeSO4 + explain quantitatively our kinetic results. We also show why the original mechanism of the Briggs-Rausher reaction must be revised and propose a variant of the mechanism proposed in 2002 by Furrow, Cervellati and Amadori. This variant establishes a relationship with the reduction of iodate by high concentrations of hydrogen peroxide and the non-catalyzed BR reaction.

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.

2017

Platinum as a HOI/I2 redox electrode and its mixed potential in the oscillatory briggs-rauscher reaction

Pt is a common redox electrode used to follow oscillations qualitatively in the Briggs-Rauscher (BR) and the Bray-Liebhafsky (BL) reactions from the time of their discovery. Although the potential oscillations of the electrode reflect the temporal pattern of the reaction properly, there is no general agreement as to how that potential is determined by the components of the reaction mixture. In this article, first we investigate how iodine species in different oxidation states affect the potential of a Pt electrode. It was found that I(+3) and I(+5) species do not affect the potential; only I-, I2, and HOI may have an influence. Although the latter three species are always present simultaneously as participants of the rapid iodine hydrolysis equilibrium, it was found that below and above the so-called hydrolysis limit potential (HLP, where the iodide and HOI concentrations are equal) the actual potential determining redox couple is different. Below the HLP, it is the traditional I2/I-redox couple, but above the HLP, it is the HOI/I2 redox pair that determines the potential of a Pt electrode. That change in the potential control mechanism was proven experimentally by exchange current measurements. In addition, from the potential response of the Pt electrode below and above the HLP, it was possible to calculate the equilibrium constant of the iodine hydrolysis as KoH = (4.97 ± 0.20) × 10-M, in rather good agreement with earlier measurements. We also studied the perturbing effect of H2O2 on the previously mentioned potentials. The concentration of H2O2 was 0.66 M, as in the BR reaction studied here. It was found that below the HLP, the perturbing effect of H2O2 was minimal but above the HLP, H2O2 shifted the mixed potential considerably down toward the HLP. In our experiments with the BR reaction, the potential oscillations of the Pt electrode crossed the HLP, indicating that from time to time the HOI concentration exceeds that of the iodide. We can conclude that although the perturbing effect of H2O2 prevents the calculation of concentrations from Pt potentials above the HLP, [I-]/[I2] ratios can be calculated as a good approximation from Pt potentials below the HLP.

2016

Historical overview of the oscillating reactions. Contribution of Professor Slobodan Anić

This review summarizes the highlights of the history of oscillating reactions since the discovery of Bray in 1917 through the discovery of Belousov, the exponential growth of the number of works in the field that followed it and chemical chaos. It focuses on the work of Professor Slobodan Anić and the Belgrade group.

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.

2014

HOI versus HOIO Selectivity of a Molten-type AgI Electrode

AgI electrode is often applied not only to det. iodine concn. but also to follow oscillations in the weakly acidic medium of the Bray-​Liebhafsky and Briggs-​Rauscher reactions where it partly follows the hypoiodous acid (HOI) concn. It is known that HOI attacks its matrix in the corrosion reaction: AgI + HOI + H+ = Ag+ + I2 + H2O and the AgI electrode measures the silver ion concn. produced in that reaction. The signal of the electrode can be the basis of sensitive and selective HOI concn. measurements only supposing that an analogous corrosive reaction between AgI and iodous acid (HOIO) can be neglected. To prove that assumption, the authors calibrated a molten-​type AgI electrode for I-​, Ag+, HOI, and HOIO in 1 M sulfuric acid and measured the electrode potential in the disproportionation of HOIO, which is relatively slow in that medium. Measured and simulated electrode potential vs. time diagrams showed good agreement, assuming that the electrode potential is detd. by the HOI concn. exclusively and the contribution of HOIO is negligible. An independent and more direct expt. was also performed giving the same result. HOIO was produced with a new improved recipe. Conclusion: an AgI electrode can be applied to measure the HOI concn. selectively above the so-​called soly. limit potential.

2013

Kinetics of iodous acid disproportionation

The iodous acid disproportionation is autocatalytic, and it is not easy to measure the rate constant of the step 2IO2H → IO3− + IOH + H+ separately. Hg(II) was used previously to suppress the autocatalytic pathway, but this method presents difficulties discussed in this work. A more effective method is the use of crotonic acid, an effective IOH scavenger. It suppresses side reactions, and a purely second-order rate law is obtained. The rate constant decreases from 5 to 0.2 M−1 s−1 when the sulfuric acid concentration increases from 0.08 to 0.60 M. The observed decrease could be explained if IO2− reacts faster than IO2H. This may have consequences for the mechanism of the oscillating Bray-Liebhafsky reaction.

Tourbillion in the phase space of the Bray-Liebhafsky nonlinear oscillatory reaction and related multiple-time-scale model

The mixed-mode dynamical states found experimentally in the concentration phase space of the iodate catalyzed hydrogen peroxide decomposition (The Bray-Liebhafsky oscillatory reaction) are discussed theoretically in a related multiple-time-scale model, from the viewpoint of tourbillion. With aim to explain the mixed-mode oscillations obtained by numerical simulations of the various dynamical states of a model for the Bray-Liebhafsky reaction under CSTR conditions, the folded singularity points on the critical manifold of the full system and Andronov-Hopf bifurcation of the fast subsystem are calculated. The interaction between those singularities causes occurrence of tourbillion structure.

2012

Kinetics of the iodate reduction by hydrogen peroxide and relation with the Briggs-Rauscher and Bray-Liebhafsky oscillating reactions

The iodate reduction by hydrogen peroxide in acidic solutions is part of the Bray-Liebhafsky and Briggs-Rauscher oscillating reactions. At low hydrogen peroxide concentrations, typical of the Bray-Liebhafsky reaction, its rate law is - d[IO3¯]/dt = (k'R + k"R [H+]) [IO3¯][H2O2] with k'R = 1.310-7 (25°), 7.810-7 (39°), 1.410 5 M-1s-1 (60°) and k"R = 1.510-5 (25°), 6.210-5 (39°), 6.310-4 M-2s-1 (60°). It is explained by a non-radical mechanism. At high hydrogen peroxide concentrations, typical of the Briggs-Rauscher reaction, a new reaction pathway appears with a rate more than proportional to [H2O2]2 and nearly independent on [IO3¯] > 0.01 M. This pathway is inhibited by scavengers of free radicals. We suggest that it has a radical mechanism starting with IOH + H2O2 IOOH + H2O and IOOH + H2O2  IO. + H2O + HOO..

2011

Iodine oxidation by hydrogen peroxide and Bray-Liebhafsky oscillating reaction

2010

Iodine oxidation by hydrogen peroxide in acidic solutions, Bray-Liebhafsky reaction and other related reactions

The kinetics of the iodine oxidation by hydrogen peroxide is a complicated function of the concentrations of iodine, hydrogen peroxide, perchloric acid and iodate. A proposed model in eight steps explains the new experimental results. It explains also the effect of the concentrations at the steady state of the hydrogen peroxide decomposition catalyzed by iodine and iodate. Without iodate added initially, the iodine oxidation by hydrogen peroxide is preceded by an induction period that depends on the oxygen concentration. A simple extension of the proposed model gives a semi-quantitative explanation of the oxygen effect and allows simulations of the Bray-Liebhafsky oscillations at 25°C.

Improvement of the stoichiometric network analysis for determination of instability conditions of complex nonlinear reaction systems

Stoichiometric network analysis (SNA), a known method for analyzing complex reaction systems including biochemical ones, is improved and applied to a nonlinear process studied far from equilibrium in a continuously fed, well stirred tank reactor (CSTR). A particular attention is focused on the determination of the narrow range of the control parameter values where the main steady state is unstable and where different dynamic states can be simulated numerically. The instability region, the most important feature of nonlinear reaction systems, is calculated as a function of the SNA parameters (current rates and reciprocal concentrations of intermediate species in the steady state) and simplified by retaining only the dominant terms. Since the number of the current rates is usually larger than the number of linearly independent equations to be used for their calculation, it is shown here that the current rates can be replaced with a smaller number of reaction rates at the steady state. These rates are related to the experimental data in a simple manner. The instability condition is also written as a function of dimensionless parameters derived from the SNA. This general approach is applied to a model of the Bray-Liebhafsky (BL) reaction having seven reactions without direct autocatalysis or autoinhibition, studied under CSTR conditions. Since the model has six intermediate species, it would be very difficult to analyze its instability condition by the conventional procedure, where a sixth order characteristic equation would have to be solved. On the other hand, the instability condition, obtained easily by the improved SNA, locates correctly the oscillatory region using numerical integration. Other dynamic states found earlier with a larger model of the BL reaction, such as mixed-mode oscillations, period doubling and chaos, are also obtained within the theoretically predicted oscillatory region. Thus, besides the general advantages of the improved stoichiometric network analysis as a method appropriate for the examination of complex nonlinear reactions, we show that the various mentioned dynamic states can be obtained by a very simple variant of the model of the BL reaction realized under CSTR conditions.

2009

Iodine(+1) Reduction by Hydrogen Peroxide

The iodine(+1) reduction by hydrogen peroxide is catalyzed by different buffers and its rate is a complicated function of the acidity and of the iodide concentration. The seemingly inconsistent published experimental results are reanalyzed and a new kinetic model is proposed. A key step is the catalysis by the buffers of the formation of the intermediate compound IOOH. This model reconciles the previous works.

2008

Inorganic Reactions of Iodine(III) in Acidic Solutions and Free Energy of Iodous Acid Formation

An analysis of the former works devoted to the reactions of I(III) in acidic non-buffered solutions gives new thermodynamic and kinetic information. At low iodide concentrations the rate law of the reaction IO3- + I- + 2 H+ = IO2H + IOH is k+B [IO3-][I-][H+]2 - k-B [IO2H][IOH] with k+B = 4.5x103 M-3s-1 and k-B = 240 M-1s-1 at 25°C and zero ionic strength. The rate law of the reaction IO2H + I- + H+ = 2 IOH is k+C [IO2H][I-][H+] - k-C [IOH]2 with k+C = 1.9x1010 M-2s-1 and k-C = 25 M-1s-1. These values lead to a Gibbs free energy of IO2H formation of - 95 kJ/mol. The pKa of iodous acid should be about 6, leading to a Gibbs free energy of IO2- formation of about - 61 kJ/mol. Estimations of the four rate constants at 50°C give respectively 1.2x104 M-3s-1, 590 M-1s-1, 2x109 M-2s-1 and 20 M-1s-1. Mechanisms of these reactions involving the protonation IO2H + H+ = IO2H2+ and an explanation of the decrease of the last two rate constants when the temperature increases, are proposed.

Stoichiometric network analysis and associated dimensionless kinetic equations. Application to a model of the Bray-Liebhafsky reaction

The stoichiometric network analysis (SNA) introduced by B.L.Clarke is applied to a simplified model of the complex oscillating Bray-Liebhafsky reaction under batch conditions, which was not examined by this method earlier. This powerful method for the analysis of steady-states stability is also used to transform the classical differential equations into dimensionless equations. This transformation is easy and leads to a form of the equations combining the advantages of classical dimensionless equations with the advantages of the SNA. The used dimensionless parameters have orders of magnitude given by the experimental information about concentrations and currents. This simplifies greatly the study of the slow manifold and shows which parameters are essential for controlling its shape and consequently have an important influence on the trajectories. The effectiveness of these equations is illustrated on two examples: the study of the bifurcations points and a simple sensitivity analysis, different from the classical one, more based on the chemistry of the studied system.

2007

Modeling Iodide-Iodate Speciation in Atmospheric Aerosols: Contributions of inorganic and organic iodine chemistry

The speciation of iodine in atmospheric aerosol is currently poorly understood. Models predict negligible iodide concentrations but accumulation of iodate in aerosol, both of which is not confirmed by recent measurements. We present an updated aqueous phase iodine chemistry scheme for use in atmospheric chemistry models and discuss sensitivity studies with the marine boundary layer model MISTRA. These studies show that iodate can be reduced in acidic aerosol by inorganic reactions, i.e., iodate does not necessarily accumulate in particles. Furthermore, the transformation of particulate iodide to volatile iodine species likely has been overestimated in previous model studies due to negligence of collision-induced upper limits for the reaction rates. However, inorganic reaction cycles still do not seem to be sufficient to reproduce the observed range of iodide - iodate speciation in atmospheric aerosol. Therefore, we also investigate the effects of the recently suggested reaction of HOI with dissolved organic matter to produce iodide. If this reaction is fast enough to compete with the inorganic mechanism, it would not only directly lead to enhanced iodide concentrations but, indirectly via speed-up of the inorganic iodate reduction cycles, also to a decrease in iodate concentrations. Hence, according to our model studies, organic iodine chemistry, combined with inorganic reaction cycles, is able to reproduce observations. The presented chemistry cycles are highly dependent on pH and thus offer an explanation for the large observed variability of the iodide - iodate speciation in atmospheric aerosol.

The State Space of a Model for the Oscillating Bray-Liebhafsky reaction

It is known from a long time that the decomposition of hydrogen peroxide catalysed by hydrogen and iodate ions, the Bray-Liebhafsky reaction, can give oscillations in a batch reactor. Recently, mixed-mode oscillations and chaos were also observed in a CSTR. The model we had proposed to explain the kinetics in a batch reactor can as well simulate these new complex behaviours. Time series give only a limited view of the features of the calculated behaviours and more information is obtained studying the properties of the state space. We use projections of the trajectories, calculation of the correlation dimension of the attractor, Poincaré sections and return maps. As the state space of the model is six-dimensional, we try to answer two questions: Do the projections into a 3D subspace give correct pictures of the real trajectories? Have we reasons to prefer a special subspace?

Kinetics of the bromate-bromide reaction at high bromide concentrations

At bromide concentrations higher than 0.1 M, a second term must be added to the classical rate law of the bromate-bromide reaction that becomes -d[BrO3-]/dt = [BrO3-][H+]2(k1[Br-] + k2[Br-]2). In perchloric solutions at 25°C k1 = 2.18 dm3.mol-3.s-1 and k2 = 0.65 dm4.mol-4.s-1 at 1 M ionic strength and k1 = 2.60 dm3.mol-3.s-1and k2 = 1.05 dm4.mol-4.s-1 at 2 M ionic strength. A mechanism explaining this rate law, with Br2O2 as key intermediate specie, is proposed. Errors that may occur when using the Guggenheim method are discussed.

Modelling iodide - Iodate speciation in atmospheric aerosol: Contributions of inorganic and organic iodine chemistry

The speciation of iodine in atmospheric aerosol is currently poorly understood. Models predict negligible iodide concentrations but accumulation of iodate in aerosol, both of which is not confirmed by recent measurements. We present an updated aqueous phase iodine chemistry scheme for use in atmospheric chemistry models and discuss sensitivity studies with the marine boundary layer model MISTRA. These studies show that iodate can be reduced in acidic aerosol by inorganic reactions, i.e., iodate does not necessarily accumulate in particles. Furthermore, the transformation of particulate iodide to volatile iodine species likely has been overestimated in previous model studies due to negligence of collision-induced upper limits for the reaction rates. However, inorganic reaction cycles still do not seem to be sufficient to reproduce the observed range of iodide - iodate speciation in atmospheric aerosol. Therefore, we also investigate the effects of the recently suggested reaction of HOI with dissolved organic matter to produce iodide. If this reaction is fast enough to compete with the inorganic mechanism, it would not only directly lead to enhanced iodide concentrations but, indirectly via speed-up of the inorganic iodate reduction cycles, also to a decrease in iodate concentrations. Hence, according to our model studies, organic iodine chemistry, combined with inorganic reaction cycles, is able to reproduce observations. The presented chemistry cycles are highly dependent on pH and thus offer an explanation for the large observed variability of the iodide - iodate speciation in atmospheric aerosol.

2006

Complex and Chaotic Oscillations in a Model for the Catalytic Hydrogen Peroxide Decomposition under Open Reactor Conditions

Numerous periodic and aperiodic dynamic states obtained in a model for hydrogen peroxide decomposition in the presence of iodate and hydrogen ions (the Bray-Liebhafsky reaction) realized in an open reactor (CSTR) where the flow rate was the control parameter, have been investigated numerically. Between two Hopf bifurcation points, different simple and complex oscillations and different routes to chaos were observed. In the region of the mixed-mode evolution of the system, the transitions between two successive mixed-mode simple states are realized by period doubling of the initial state leading to a chaotic window in which the next dynamic state emerges mixed with the initial one. It appears in increasing proportions in concatenated patterns until total domination. Thus, with increasing the flow rate the period-doubling route to chaos, whereas with decreasing the flow rate, the peak-adding route to chaos was obtained. Moreover, in very narrow regions of flow rates, chaotic mixtures of mixed-mode patterns were observed. This evolution of patterns repeats until the end of the mixed-mode region at high flow rates that corresponds to chaotic mixtures of one large and many small amplitude oscillations. Starting from the reverse Hopf bifurcation point and decreasing the flow rate, simple small amplitude sinusoidal oscillations were encountered and then the period doubling route to chaos. With further decreasing flow rate, the mixed mode oscillations emerge inside the chaotic window.

2005

What is a reaction rate?

Experimentally, we measure rates of reactant consumption or rates of product formation. These rates are related to, but different from, reaction rates. A reaction rate is a property of a given reaction, not of chemical species. The relationships between these two kinds of rates are not always simple. In a homogeneous closed reactor, a correct definition of a reaction rate is (dx/dt)/V, where V is the reactor volume and x the extent of reaction. Open systems require a different approach to the concept of reaction rate and there is no simple equation that can be used as a general definition in all kinds of reactors. We propose a definition leading always and simply to the correct equations.

2004

Inorganic reactions of iodine(+1) in acidic solutions

We present a thorough analysis of the former works concerning the hydrolysis of iodine and its mechanism in acidic or neutral solutions and recommend values of equilibrium and kinetic constants. Since the literature value for the reaction H2OI+ ⇌ HOI + H+ appeared questionable, we have measured it by titration of acidic iodine solutions with AgNO3. Our new value, K(H2OI+ ⇌ HOI + H+) ∼ 2 M at 25°C, is much larger than accepted before. It decreases slowly with the temperature. We have also measured the rate of the reaction 3HOI → IO3− + 2I− + 3H+ in perchloric acid solutions from 5 × 10−2 M to 0.5 M. It is a second order reaction with a rate constant nearly independent on the acidity. Its value is 25 M−1 s−1 at 25°C and decreases slightly when the temperature increases, indicating that the disproportionation mechanism is more complicated than believed before. An analysis of the studies of this disproportionation in acidic and slightly basic solutions strongly supports the importance of a dimeric intermediate 2HOI ⇌ I2O·H2O in the mechanism. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36:480-493, 2004

2002

pH of Sodium Acetate Solutions

2001

The oxidation of iodine to iodate by hydrogen peroxide

2000

Thermodynamic consistency of reaction mechanisms and null cycles

The illustration of multistability

Kinetics of the Dushman reaction at low I- concentrations

1999

Kinetics and mechanism of the iodate-iodide reaction and other related reactions

Effects of oxygen on the Bray-Liebhafsky reaction

1997

Simulation of iodine oxidation by hydrogen peroxide in acid media on basis of the model of the Bray-Liebhafsky reaction

The kinetics of iodine oxidation by hydrogen peroxide in acid media has been investigated. The Bray-Licbhafsky oscillatory reaction takes place in the same reaction system and the process of iodine oxidation by hidrogen peroxide presents an important part of its mechanism. The dependence of the rate of iodine oxidation on the initial value of the hydrogen peroxide concentration, [H2O2]0, and the existence of an unusual phenomenon, the maximum value of the experimentally found reaction rate constant, in respect to [H2O2]0 have been successfully simulated on the basis of a kinetic model of the Bray-Licbhafsky reaction.

Pseudo-steady states in the model of the Bray-Liebhafsky oscillatory reaction

1996

Formation et décomposition de complexes

1994

The uncertainty of pH

1992

Mechanism of the Bray-Liebhafsky Reaction

1991

Etude du Braylator par la méthode de Clarke

1988

Cinétique et mécanisme des réactions bromate-chlorite et bromate-dioxyde de chlore

1987

Mécanisme des réactions du chlorite et du dioxyde de chlore

In acidic solutions of chlorite and bromide two processes occur simultaneously, the disproportionation of chlorite and an autocatalytic reaction leading to a rapid production of C102. The unusual features of this reaction are described. In this complex system the rate of HClO2+ Br-+ H++ HClO + HBrO cannot be measured. It can be, however, with added ortho-tolidine to remove the HBrO and HClO. We obtained r = k [[]HClO2][[]Br-] [[]H+] with k = 1.48 × 10-2M-1at 25°C. Without added ortho-tolidine this reaction initiates the autocatalytic reaction for which we suggest a kinetic scheme.

Cinétique de la réaction de Bray

1986

Mécanisme des réactions du chlorite et du dioxyde de chlore

Utilisation de l'ortho-tolidine pour l'étude des réactions des halogénates et halogénites

We have shown previously that oft/iotolidine greatly simplifies the kinetic study of redox reactions of chlorite by reacting with intermediate products and eliminating side reactions. The present study shows the validity of the method in the case of bromate reactions. For the bromate-bromide reaction it gives the classical fourth-order rate law with k = 1.54 M"3s-1 in perchloric acid solutions at 25°C and 1 M ionic strength, and an acidity constant of bromic acid of 2.9. This method is then used to study the reaction between bromate and chlorite, a complex reaction in the absence of ortho-tolidine. The rate law is d[BrO3-]/dt=k[BrO3-][HClO2][H+] with k = 0.83 + 0.76 [H+] in the same conditions. If [H+] = 0.1 M the apparent activation energy is 47.4 kJ/mol.

1985

Mécanisme des réactions du chlorite et du dioxyde de chlore

1984

Mécanisme des réactions du chlorite et du dioxyde de chlore

1981

Etude des données conductimétriques relatives aux solutions de HIO3, KIO3 et NaIO3

Mécanisme des réactions du chlorite et du dioxyde de chlore

1980

Compétition entre déshydratation et amination du méthanol sur silice-alumine

1979

Valeurs thermodynamiques du chlorite et du dioxyde de chlore en solution

1978

Déshydratation du méthanol sur silice-alumine

1977

Réaction oscillante de Belousov

1976

Réaction oscillante de Belousov

1975

Cinétique de la synthèse de la monométhylamine

1974

Oscillations entretenues dans un système chimique homogène

1973

Schémas réactionnels oscillants en phase homogène

Communications publiées lors de congrès ou colloques nationaux et internationaux

2022

Role of Radicals in the Bray-Liebhafsky Reactions

2014

Iodine Inorganic Reactions In Acidic Solutions And Oscillating Reactions

2012

The Bray-Liebhafsky and Briggs-Rauscher oscillating reactions

2011

Critical manifold of an oscillatory reaction model with more than one fast variable

2010

Clock Reactions

Clock behaviours, resulting from transitions between different dynamical states, are observed in many different chemical systems. Some examples are discussed and compared: the Landolt reaction, the oxidation of Ce(III) by bromate, the reduction of iodate by hydrogen peroxide and the oxidation of iodine by hydrogen peroxide in the absence of iodate. In the last case, the bell rings when a stable steady state suddenly disappears.

Critical manifold of the model for the Bray-Liebhafsky oscillatory reaction

Mixed mode oscillations are obtained in numerical simulations of the Bray-Liebhafsky oscillatory reaction in CSTR, for appropriate choice of the parameter set. In this paper, we analyze critical manifold of the slow-fast system in three dimensional phase subspace. We found that small amplitude oscillations obtained as a part of mixed mode dynamics are governed by canard solutions.

2006

Complex Oscillations and Chaos in Spaces with more than Three Dimensions

2004

Modelling the Bray-Liebhafsky reaction

Simulation of Complex Oscillations Based on a Model of the Bray-Liebhafsky reaction

2002

Thermodynamics and Kinetics of Some Inorganic Reactions of Iodine

2000

Kinetics of the Halates-Halides-Halogens reactions

1998

Different Variants of the Model for the Bray-Liebhafsky Reaction Analysed by Means of the Steady States and Corresponding Nullclines

Activation energy of iodine oxidation, determined experimentally and on the basis of numerical simulations

Models for oscillating reactions, nullclines and steady states

1996

Dependence of the rate of iodine oxidation by hydrogen peroxide on the acidity of the Bray-Liebhafsky system

Numerical simulation of the iodine oxidation by hydrogen peroxide in the Bray-Liebhafsky system at 298K

1990

Transient Behaviours in the Bray Liebhafsky Reaction

1984

Mécanisme de la réaction de Bray

1979

Etude cinétique de la réaction de Bray