Batch pH Oscillations in the BelousovâZhabotinsky Reaction - The

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A: Kinetics, Dynamics, Photochemistry, and Excited States

Batch pH Oscillations in the Belousov-Zhabotinsky Reaction Glen A. Frerichs, James Jones, Xiaohe Huang, Mulurhab Gebrekidan, Jacob Burch, Mei (Yuan) Cheng, and Yuwei Chen J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.8b11222 • Publication Date (Web): 23 Jan 2019 Downloaded from http://pubs.acs.org on January 29, 2019

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The Journal of Physical Chemistry

Batch pH Oscillations in the BelousovZhabotinsky Reaction Glen A. Frerichs,*,+ James Jones+, Xiaohe Huang+, Mulurhab Gebrekidan+, Jacob Burch+, Mei Yuan Cheng+, and Yuwei Chen+ + Department of Chemistry, Westminster College, 501 Westminster Ave, Fulton, MO 65251 Email: [email protected] Phone: 573-592-5205

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The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Abstract No single-phase system has been reported previously to give significant pH oscillations in a closed (batch) reactor. We report here sustained pH oscillations in batch for the Belousov-Zhabotinsky (BZ) reaction using much lower [H+]0 and much higher [BrO3-]0 than in traditional studies of this reaction. In fact, pH oscillations were obtained in the presence of only BrO3-, malonic acid (MA), and Mn2+. The amplitude, frequency, and duration of oscillations tend to depend primarily on the ratio of [BrO3-]0 to [MA]0. A critical part of the proposed mechanism involves reversible formation of a manganese(III) complex with bromomalonic acid, followed by two-electron oxidation to tartraric acid and Mn2+. Estimates of the corresponding rate constant values for these reactions have been obtained by simulation. It is suggested that the presence of a supercatalytic reaction in H+ may be a sufficient, if not necessary, requirement for the occurrence of pH oscillations in a batch system.

Introduction


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Batch chemical oscillators are extremely rare, with the Bray-Liebhafsky and BelousovZhabotinsky reactions being arguably the most well known. The first homogeneous chemical oscillator, consisting of H2O2, KIO3, and H2SO4, was reported by Bray1 in 1921 and was studied subsequently by Liebhafsky.2 The Briggs-Rauscher oscillatory reaction also incorporates these same reactants, along with malonic acid and manganous ion. Upon addition of starch indicator, this reaction is the basis for arguably the most dramatic demonstration of color changes in oscillating systems.3 The Bray-Liebhafsky (BL) and Briggs-Rauscher (BR) reactions have been found to oscillate both in a closed system (batch) and in a continuous-flow stirred tank reactor (CSTR). In 1951, the Belousov-Zhabotinsky (BZ) oscillator was discovered by Belousov.4 Zhabotinsky reinvestigated this batch reaction a decade later.5 Subsequently, the BZ reaction was shown also to oscillate in a CSTR. The classical BZ system is the most studied chemical oscillator and consists of BrO3-, malonic acid (MA), and cerium (IV) ions as a catalyst in H2SO4. A simpler chemical system known as the minimal bromate (MB) oscillator was found by Orban et al.6 to oscillate in a CSTR (but not in batch) over an extremely narrow range of conditions. The MB oscillator consists of BrO3-, Br-, and either cerium or manganese ions, in H2SO4. The batch systems mentioned above generally give oscillations in absorbance at a fixed wavelength, or in potential of a Pt or specific-ion electrode versus a reference electrode. Considerable efforts to discover chemical systems that exhibit pH oscillations in a closed system have met with very limited success. In the case of three such reported systems, the pH changes hardly exceeded the experimental error. These systems involved the thermal decomposition of aqueous sodium dithionite,10 the BL reaction,11 and the BZ reaction.12 The iodate-thiosulfate-sulfite batch reaction in H2SO4 is capable of giving



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large-amplitude pH oscillations, but they are strongly damped (typically lasting only 2 or 3 periods at most).13 Similar results have been obtained by Frerichs et al.14 for the acidic chlorite-sulfite closed system.

Rationale Horvath has explained the behavior of the iodate-thiosulfate-sulfite system by showing that the rate equation for the reaction of iodate with sulfite in H2SO4 has a term that exhibits second order dependence on hydrogen ion (autocatalyst).15 Such a reaction exhibiting second order or higher dependence on hydrogen ion is referred to as supercatalytic in hydrogen ion. Both the BZ reaction16,17 and the MB oscillator18,19 are thought to have the same initial rate-determining step: BrO3- + Br- + 2 H+ HBrO2 + HOBr

(R1)

Presumably, this also would be the case for the simple bromate-bromide-sulfuric acid batch system. The rate law for R1 is: vR1 = kR1 [BrO3-][Br-][H+]2. Similarly, the Dushman reaction20-22 (which is also assumed to be an important reaction in the BL and BR oscillators) involves the rate-determining step: IO3- + I- + 2 H+ HIO2 + HOI

(R2)

for which the rate law is: vR2 = kR2 [IO3-][I-][H+]2. Since both the bromate-bromidesulfuric acid and the iodate-iodide-sulfuric acid systems apparently involve a supercatalytic reaction in which the rate depends on the square of the hydrogen ion concentration, it is tempting to hypothesize that the presence of a supercatalytic reaction may be a sufficient, if not necessary, requirement for pH oscillations to occur in batch. As a test of the above hypothesis, we have carried out an experimental study of the acidic bromate-bromide and iodate-iodide closed systems. Results are discussed below.


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In a kinetic study of the acidic bromate-iodide reaction Simoyi et al.23,24 found evidence for a rate-determining supercatalytic reaction that is second order in hydrogen ion: BrO3- + I- + 2 H+ HBrO2 + HOI

(R3)

The rate law for this reaction is: vR3 = kR3 [BrO3-][I-][H+]2. The kinetics of the reduction of iodate by bromide in the presence of phenol has been studied by Sharma and Gupta.25 Phenol is not oxidized by the iodate under the acidic conditions used, but it reacts with the products, iodite and bromine, to prevent the formation of the usual end products of the iodate-bromide reaction. The slow step is: IO3- + 2 Br- + 2 H+ IO2- + Br2 + H2O

(R4)

Even under these simplifying conditions, a two-term rate law was obtained that was first order in IO3-, second order in Br-, and that showed a complex dependence on [H+]. The apparent order found with respect to hydrogen ion was 2.6, suggesting second order dependence for one term and third order dependence for the other. Because of the supercatalytic nature of R3 and R4, it was decided also to investigate the acidic bromate-iodide and iodate-bromide systems in batch. Interestingly, we have observed oscillations in both pH and potential in all four acidic halate-halide systems: BrO3--Br-; IO3--I-; BrO3--I-; and IO3--Br-.26 These results were found primarily at elevated temperatures, generally 60oC. After discovering that the acidic iodate-iodide system (a subsystem of the BL system) gave batch pH oscillations, it seemed likely that such oscillations could be obtained also with the BL reaction. Thus, we decided to study the BL reaction in a closed system and have found pH oscillations at 60oC.26 Likewise, since the BR reaction includes components of both the BL and BZ reactions, we also studied this system in batch. In this case, we obtained pH oscillations at both 40oC and 60oC.26 The above successes led



us to search for pH oscillations in the batch BZ reaction, which is the main subject of this report.

Experimental For the study of the BZ reaction in batch, experiments generally were carried out either in a Plexiglas CSTR with total solution volume of 35 mL or in a glass batch reactor covered by a reactor cap and having a total solution volume of 40 mL. Both the CSTR and batch reactors had a small opening in the reactor cap. A combination pH electrode and a Pt electrode, each with a Ag/AgCl reference electrode, were inserted in the reactor cap. Both pH and potential were recorded concurrently using either a Servogor 124 or a Kipp Zonen BD41chart recorder, each with pens offset. Stirring was done at a rate of 500-550 rpm using a Teflon coated stir bar and a Fisher Scientific stirrer. Runs were carried out at room temperature, (21+/-0.5)oC, as well as at 25oC and 60oC using a constant-temperature circulator. The reagents NaBrO3 (Fisher), malonic acid (Acros), and MnSO4 . H2O (Fisher) were used in solid form. Initially, experiments were done with solid KBrO3 (Fisher), but later NaBrO3 was used because of its greater solubility. Runs were carried out in the presence of H2SO4, NaOH, or neither. All reagents were ACS-certified. Solid reagents were dissolved in water (with MnSO4 . H2O added last) to give the desired total volume. Ultrapure water for solutions was bubbled with N2 for about an hour prior to use.

Results Oscillations in pH were obtained in the batch BZ reaction at room temperature, as well as at 25 oC and 60oC, over a wide range of concentrations (Table 1). Typical results are shown in Figures 1-4. Generally, oscillations in both pH and potential occurred concurrently. Virtually simultaneously, the solution turned a dark brown color


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and there was a sharp drop in pH. Then, as the pH gradually increased, the color of the solution became much lighter. Depending on the concentrations of the main reactants, pH oscillations were obtained with H2SO4, with NaOH, or with neither present. This is very much unlike traditional studies of the BZ reaction that are generally done with high [H2SO4]0. Conditions favoring pH oscillations also involve significantly higher [BrO3-]0 than in traditional studies. Initially, experiments were conducted in the presence of H2SO4, and it was found necessary to use relatively low [MA]0 in order to obtain pH oscillations. Then, a series of runs was carried out using NaOH. In this case, relatively high [MA]0 was required in order to observe oscillations. Finally, it was decided to determine if oscillations could be obtained with only the initial reactants of NaBrO3, MA, and MnSO4 present. This attempt was quite successful using intermediate levels of [MA]0. Because this was a simpler system, eventually this became the method of choice. The maximum amplitude observed for pH oscillations was 0.81 pH unit, and that for potential oscillations was on the order of 200 mV. Maximum duration of oscillations was 5 hr, and oscillatory periods ranged from 30 s to 40 min. The case could be made very generally that higher ratios of [BrO3-]0 to [MA]0 tend to lead to oscillations with fewer peaks of larger amplitude; lower ratios tend to yield extended oscillations with peaks of smaller amplitude. This trend is shown rather dramatically in comparing Figures 3 and 4. In Figure 3, the ratio of [BrO3-]0 to [MA]0 is 11:1, while in Figure 4, the ratio of [BrO3-]0 to [MA]0 is 4:1. However, [Mn2+]0, and possibly [H2SO4]0 or [NaOH]0, could affect the overall generalization. To be sure of this generalization, one would need to fix the initial concentration(s) of any other reactant(s) while varying [BrO3-]0 and [MA]0 in a series of runs.



Because other organic acids and catalysts have been found to give oscillations in potential with the BZ reaction under traditional conditions, two additional series of runs were done at room temperature. With citric acid (CA) substituted for MA, oscillations in potential were obtained, but not in pH. Attempts were made to obtain pH oscillations with Ce(NH4)2(NO3)6 in place of MnSO4, again using MA. Although numerous runs gave sustained oscillations in both potential and pH, the maximum amplitude for the latter was only 0.03 pH unit. A possible reason for the lack of effectiveness of Ce(IV) relative to Mn(II) in producing significant pH oscillations will be mentioned below.

Discussion To account for the observed pH oscillations in the batch BZ system, we propose the model shown in Table 2. This model can be considered to include mechanisms for three different subsystems. The first subsystem is referred to as the Minimal Bromate Subsystem, the second is designated the Bromine-Malonic Acid Subsystem, and the third is identified as the Manganese-Bromomalonic Acid Subsystem. The model for the Minimal Bromate Subsystem is the NFT mechanism,16 as used previously for both the traditional BZ oscillator17 and the minimal bromate oscillator.18,19 Similarly, the reaction steps for the Bromine-Malonic Acid Subsystem have been used previously as part of the mechanism for the traditional BZ oscillator.27 The rate constants given in Table 2 for the Minimal Bromate Subsystem and Bromine-Malonic Acid Subsystem are based on previously published values.27,28 The mechanism for the Manganese-Bromomalonic Acid Subsystem is based primarily on kinetic studies by Tikhonova et al.29 on the oxidation of MA by bromate ion, catalyzed by manganese ion, in sulfuric acid solutions. We propose reversible formation of a manganese(III) complex with bromomalonic acid (BrMA), followed by two-electron


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oxidation to tartronic acid (TA) and Mn2+. The rate constants listed in Table 2 for the Manganese-Bromomalonic Acid Subsystem were obtained by treating them as variable parameters in computer simulations using the given model. Computer simulations based on the model in Table 2 were carried out with Berkeley Madonna software using the Rosenbrock method for integrating stiff differential equations. Simulations reproduced the general features of experimental pH oscillations (Figure 5) and also generated periodic oscillations (Figure 6) in the concentrations of other species, such as Br- and [Mn(III)BrMA]+. For the purpose of these simulations, [Br-]0 was based on the percentage of bromide impurity in the sodium bromate source. When MA was the only acid present in the original reaction mixture, [H+]0 was calculated from the first ionization step using pKa1 = 2.847.30 Based on the results of simulations, [Mn3+] should be low enough to allow one to neglect the contribution of its hydrolysis toward [H+]. Prior to discovering that the Manganese-Bromomalonic Acid Subsystem is required for simulations to give pH oscillations, we first attempted to model our results using the Manganese-Malonic Acid Subsystem. The mechanism we used is based on a kinetic study by Kemp and Waters31 on the oxidation of malonic acid by manganese(III) sulfate. The reaction steps proposed are given below. (M1) Mn3+ + MA [Mn(III)MA]+ + 2H+ (M2) Mn3+ + [Mn(III)MA]+ [Mn(IV)MA]2+ + Mn2+ (M3) [Mn(IV)MA]2+ + H2O ---> TA + Mn2+ This subsystem consists of the reversible formation of the Mn(III) complex of MA, followed by reversible formation of the Mn(IV) complex of MA, and then irreversible



oxidation of MA to TA and reduction of Mn(IV) to Mn2+. Attempts to obtain simulated oscillations by including the Manganese-Malonic Acid Subsystem were unsuccessful. Also, omitting the subsystem did not have any effect on the computer simulations after we realized we needed to include the ManganeseBromomalonic Acid Subsytem. Apparently, the contributions of the Mn(III) and Mn(IV) complexes of MA to the overall reaction are negligible. According to the model in Table 2, the BZ reaction is initiated by step (1), which requires involvement of bromide impurities in the bromate source. Elemental bromine is formed in step (3). It is consumed by hydrolysis in the reverse reaction and by reaction with ENOL to form BrMA in step (9). Both of the latter processes in turn regenerate Bralong with H+. Meanwhile, Mn3+ is formed in step (5) by oxidation of Mn2+ with BrO2, and then reacts reversibly with BrMA in step (11) to form the brown Mn(III) complex, [MnBrMA]+, along with more H+. This likely accounts for the nearly simultaneous sharp drop in pH and formation of a brown color in the solution. Then, as the two-electron oxidation reaction in step (12) takes place between Mn3+ and [MnBrMA]+, the solution color gradually turns lighter. At the same time, Br- is produced, and the pH gradually increases due to consumption of H+ in steps (1)–(5) as the cycle repeats itself. In order to support the suggestion that [MnBr(III)MA]+ is the species responsible for the observed color change, we carried out a spectrophotometric study on the BZ system. Periodic oscillations of absorbance were obtained over the range of 400-480 nm, with maximum absorbance at 450 nm.32 Although we are not aware of any literature value of lmax for [Mn(III)BrMA]+, our result does provide evidence that Br2 is not responsible for any significant part of the absorbance. The value of lmax for the latter is 400 nm, not 450 nm.33 Also, simulations show that Br2, along with other species that could possibly


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contribute to the absorbance, are at too low a concentration to be a factor. It should be noted that formation of gas bubbles provided evidence of oxidation of TA ultimately to CO2, suggesting that intermediate acids such as oxalic acid and formic acid, were also formed. Nevertheless, even without these oxidation products being included, computer simulations gave a relatively good correlation with measured oscillations. In the future, attempts will be made to determine what effect, if any, inclusion of further oxidation steps may have on simulations.

Conclusions This system appears to be the first single-phase batch oscillator reported to give sustained pH oscillations of significant amplitude. Both the duration of oscillations and their maximum amplitude depend directly on the [BrO3-]0/[MA]0 ratio. This oscillator differs from the traditional BZ oscillator in that it involves much lower concentrations of acid and generally higher concentrations of bromate. In fact, the only acid source can be MA. In this case, one need only dissolve three solids in water to obtain oscillations in pH, in potential, and in absorbance. Such a simple procedure suggests that this system lends itself to use in chemical demonstrations and to experiments in teaching laboratories. The model we propose to account for the pH oscillations involves three subsystems. Both the Minimal Bromate and the Bromine-Malonic Acid subsystems involve the same reaction steps and rate constant values as in the traditional BZ oscillator. The critical component of our model, however, is the proposed Manganese-Bromomalonic Acid Subsystem. The latter involves reversible formation of a manganese(III) complex with BrMA, followed by two-electron oxidation to TA and Mn2+. Inclusion of this subsystem accounts for the formation of pH oscillations in our simulations; without it, none are observed. Our simulations also allow an estimate of the rate constant values (k11, k-11, and



k12) corresponding to the proposed reaction steps in the Manganese-Bromomalonic Acid Subsystem. The lack of effectiveness of Ce(IV) relative to Mn(II) in producing significant pH oscillations was mentioned above. Perhaps this could be due to an inability of Ce(IV) to form a complex with BrMA similar to that for manganese. We suggested above the hypothesis that the presence of a supercatalytic reaction in H+ may be a sufficient, if not necessary, requirement for pH oscillations to occur in a batch system. At the very least, one can state the results of the present study are consistent with this hypothesis. This suggests that, in searching for further systems that give significant pH oscillations in batch, it may be fruitful to investigate those systems thought to involve a supercatalytic reaction. Numerous investigations of the traditional BZ oscillator in a continuous flow stirred tank reactor (CSTR) have been done. One of the fascinating phenomena resulting from these studies has been the existence of complex dynamical behavior, including chaos. It would be interesting to see if such behavior would be observed if the present system were studied in a CSTR, where the flow rate would be an additional variable parameter.

Acknowledgment One of us (GAF) wishes to thank Richard C. Thompson, Professor Emeritus in the Department of Chemistry at the University of Missouri-Columbia, for allowing the use of his laboratory for early research on oscillating chemical reactions during the author’s sabbatical leave, as well as for Prof. Thompson’s collaboration over the years. We also thank Westminster College for its support of undergraduate research. Finally, we wish to acknowledge the helpful technical assistance provided by Cadnel Detchou and Christopher W. Frerichs. Table 1


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Initial reactant concentrations and results at 60oC in presence of H2SO4 [BrO3-], M 1.80 1.80 2.00 1.50 1.50

[MA], M 0.150 0.150 0.200 0.150 0.150

[MnSO4], M 0.0600 0.0600 0.0200 0.0600 0.0600

[H2SO4], M 1.00 x 10-3 2.00 x 10-2 1.13 x 10-2 5.00 x 10-4 2.00 x 10-2

No. Oscs. 4 8 5 3 6

Max. Ampl. (pH Unit) 0.63 0.44 0.75 0.39 0.59

Initial reactant concentrations and results at 60oC in presence of NaOH [BrO3-], M

[MA], M

[MnSO4], M

[NaOH], M

No. Oscs.

1.50 1.50 1.50 1.50 1.50 1.50 1.50 2.00 1.50 1.80 1.50 1.20 1.20 1.00 0.900 0.900 0.800 0.800

0.400 0.500 0.600 0.750 0.750 0.750 1.00 1.50 1.20 1.50 1.50 1.50 1.75 1.50 1.50 1.50 1.50 1.50

0.0500 0.0500 0.0300 0.0300 0.0300 0.0400 0.0300 0.0400 0.0300 0.0360 0.0300 0.0240 0.0240 0.0200 0.0150 0.0170 0.0150 0.0150

0.00500 0.0100 0.0300 0.0700 0.0600 0.0500 0.0900 0.0900 0.0900 0.0900 0.0900 0.0900 0.0100 0.0900 0.0900 0.0900 0.0900 0.0700

4 8 8 3 4 6 6 17 13 13 16 13 15 13 11 9 7 8

Max. Ampl. (pH Unit) 0.42 0.40 0.27 0.34 0.35 0.31 0.22 0.16 0.14 0.13 0.13 0.13 0.09 0.10 0.08 0.09 0.08 0.08

Initial reactant concentrations and results at 60oC in absence of H2SO4 or NaOH [BrO3-], M 2.25 2.50 2.00 2.50 2.70 2.00 1.80 1.80 1.80 1.50 1.75

[MA], M 0.150 0.200 0.200 0.250 0.270 0.250 0.240 0.300 0.300 0.300 0.500

[MnSO4], M 0.0600 0.0500 0.0600 0.0500 0.0500 0.0500 0.0600 0.0500 0.0300 0.0500 0.0600

No. Oscs. 4 5 6 6 10 6 5 6 8 5 7


Max. Ampl. (pH Unit) 0.44 0.44 0.49 0.39 0.34 0.46 0.47 0.46 0.47 0.44 0.39


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Initial reactant concentrations and results at room temperature in absence of H2SO4 or NaOH [BrO3-], M 2.20 2.20 2.20 2.10 2.50 2.10 2.00 2.00 2.00

[MA], M 0.200 0.200 0.200 0.350 0.550 0.500 0.500 0.500 0.500

[MnSO4], M 0.0900 0.100 0.150 0.060 0.0200 0.400 0.100 0.300 0.325

No. Oscs. 5 5 4 11 40 4 19 5 5

Max. Ampl. (pH Unit) 0.65 0.49 0.35 0.36 0.12 0.48 0.43 0.81 0.76

Initial reactant concentrations and results at 25oC in absence of H2SO4 or NaOH [BrO3-], M 2.20 2.10 2.20 2.15 2.15 2.15 2.10 2.20

[MA], M 0.200 0.200 0.300 0.350 0.350 0.350 0.350 0.836

[MnSO4], M 0.0900 0.0900 0.0900 0.0600 0.0700 0.0400 0.0400 0.0360

No. Oscs. 5 4 4 8 3 4 16 33

Max. Ampl. (pH Unit) 0.40 0.35 0.50 0.29 0.43 0.40 0.33 0.20

Table 2 Model for BZ Batch pH Oscillator Minimal Bromate Subsystem (1) BrO3- + Br- + 2H+ HBrO2 + HOBr

k1 = 2.1 M-3s-1; k-1 = 1 x 104 M-1s-1

(2) HBrO2 + Br- + H+ 2HOBr

k2 = 2 x 109 M-2s-1; k-2 = 5.0 x 10-5 M-1s-1

(3) HOBr + Br- + H+ Br2 + H2O

k3 = 8 x 109 M-2s-1; k-3 = 110 s-1

(4) BrO3- + HBrO2 + H+ 2BrO2 + H2O

k4 = 1 x 104 M-2s-1; k-4 = 2.0 x 107 M-1s-1

(5) Mn2+ + BrO2 + H+ Mn3+ + HBrO2

k5 = 1.8 x 105 M-2s-1; k-5 = 2.4 x 107 M-1s-1

(6) Mn3+ + BrO2 + H2O Mn2+ + BrO3- + 2H+

k6 = 35 M-1s-1; k-6 = 1.3 x 10-4 M-3s-1

(7) 2HBrO2 BrO3- + HOBr + H+

k7 = 4 x 107 M-1s-1; k-7 = 2.1 x 10-10 M-2s-1


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Bromine-Malonic Acid Subsystem (8) MA ENOL

k8 = 3.0 x 10-3 s-1; k-8 = 200 s-1

(9) ENOL + Br2 ---> BrMA + Br- + H+

k9 = 1.91 x 106 M-1s-1

(10) MA + HOBr ---> BrMA + H2O

k10 = 8.2 M-1s-1

Manganese-Bromomalonic Acid Subsystem (11) Mn3+ + BrMA [Mn(III)BrMA]+ + 2H+

k11 = 5 x 106 M-1s-1; k-11 = 2 x 105 M-2s-1

(12) Mn3+ + [Mn(III)BrMA]+ ---> TA + 2Mn2+ + Br- + H+ k12 = 1 x 104 M-1s-1

Abbreviations: MA ~ CH2(COOH)2 ~ malonic acid ENOL ~ (HOOC)CH=C(OH)2 BrMA ~ BrCH(COOH)2 ~ bromomalonic acid TA ~ HCOH(COOH)2 ~ tartronic acid



Figure 1


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Figure 2



Figure 3


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Figure 4



Figure 5


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Figure 6

References (1) Bray, W. C. A Periodic Reaction in Homogeneous Solution and its Relation to Catalysis. J. Am. Chem. Soc. 1921, 43, 1262-1267. (2) Bray, W. C.; Liebhafsky, H. A. Reactions Involving Hydrogen Peroxide, Iodine, and Iodate ion. I. Introduction. J. Phys. Chem. 1931, 53, 38-48.



(3) Briggs, T. S.; Rauscher, W. C. An Oscillating Iodine Clock Reaction. J. Chem. Ed. 1973, 50, 496. (4) Belousov, B. P. A Periodic Reaction and its Mechanism, in Oscillations and Traveling Waves in Chemical Systems (Field, R. J.; Burger, M., Eds.), Wiley: New York, 1985; p 605-613. (5) Zhabotinsky, A. M. Periodic Kinetics of Oxidation of Malonic Acid in Solution (Study of the Belousov Reaction Kinetics). Biofizika 1964, 9, 306-311. (6) Orban, M.; De Kepper, P.; Epstein, I. R. Minimal Bromate Oscillator: BromateBromide-Catalyst. J. Am. Chem. Soc. 1982, 104, 2657-2658. (7) De Kepper, P.; Epstein, I. R.; Kustin, K.; Orban, M. Batch Oscillations and Spatial Wave Patterns in Chlorite Oscillating Systems. J. Phys. Chem. 1982, 86, 170-171. (8) Lengyel, I.; Rabai, Gy.; Epstein, I. R. Batch Oscillation in the Reaction of Chlorine Dioxide with Iodine and Malonic Acid. J. Am. Chem. Soc. 1990, 112, 4606-4607. (9) Horvath, A. K.; Nagypal, I.; Epstein, I. R. Oscillatory Photodecomposition of Tetrathionate Ion. J. Am. Chem. Soc. 2002, 124, 10956-10957. (10) Rinker, R. G.; Lynn, S.; Mason, D. M.; Corcoran, W. H. Kinetics and Mechanism of the Thermal Decomposition of Sodium Dithionite in Aqueous Solution. Ind. Eng. Chem. Fundam. 1965, 4, 282-288. (11) Matsuzaki, I.; Woodson, J. H.; Liebhafsky, H. A. pH and Temperature Pulses during the Periodic Decomposition of Hydrogen Peroxide. Bull. Chem. Soc. Jpn. 1970, 43, 3317. (12) Tsukada, M. Belousov-Zhabotinskii Oscillating Reaction without Strong Acid Such as Sulfuric Acid. Chem. Lett. 1987, 1707-1710. (13) Rabai, Gy.; Beck, M. T. Exotic Chemical Phenomena and their Chemical Explanation in the Iodate-Sulfite-Thiosulfate System. J. Phys. Chem. 1988, 92, 2804-2807. (14) Frerichs, G. A.; Mlnarik, T. M.; Grun, R. J.; Thompson, R. C. A New pH Oscillator: The Chlorite-Sulfite-Sulfuric Acid system in a CSTR. J. Phys. Chem. A 2001, 105, 829-837. (15) Horvath, A. K. Revised Explanation of the pH Oscillations in the IodateThiosulfate-Sulfite System. J. Phys. Chem. A, 2008, 112, 3935-3942.


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(16) Noyes, R. M.; Field, R. J.; Thompson, R. C. Mechanism of Reaction of Br(V) with Weak, One-Electron Reducing Agents. J. Am. Chem. Soc. 1971, 93, 73157316. (17) Field, R. J.; Koros, E.; Noyes, R. M. Oscillations in Chemical Systems. II. Thorough Analysis of Temporal Oscillations in the Bromate-Cerium-Malonic Acid System. J. Amer. Chem. Soc. 1972, 94, 8649-8664. (18) Geiseler, W.; Bar-Eli, K. Bistability of the Oxidation of Cerous Ions by Bromate in a Stirred Flow Reactor. J. Phys. Chem. 1981, 85, 908-914. (19) Bar-Eli, K.; Geiseler, W. Perturbations Around Steady States in a Continuous Stirred Tank Reactor. J. Phys. Chem. 1983, 87, 1352-1357. (20) Dushman, S. The Rate of the Reaction between Iodic and Hydriodic Acids. J. Phys. Chem. 1903, 8, 453-482. (21) Schmitz, G. Kinetics and Mechanism of the Iodate-Iodide Reaction and other Related Reactions. Phys. Chem. Chem. Phys. 1999, 1, 1909-1914. (22) Agreda B., J. A.; Field, R. J.; Lyons, N. J. Kinetic Evidence for Accumulation of Stoichiometrically Significant Amounts of H2I2O3 during the Reaction of I- with IO3-. J. Phys. Chem. A 2000, 104, 5269-5274. (23) Simoyi, R. H.; Masvikeni, P.; Sikosana, A. Complex Kinetics in the BromateIodide Reaction: A Clock Reaction Mechanism. J. Phys. Chem. 1986, 90, 41264131. (24) Chinake, C. R.; Simoyi, R. H. Kinetics and Mechanism of the Complex Bromate-Iodine Reaction. J. Phys. Chem. 1996, 100, 1643-1656. (25) Sharma, D. N.; Gupta, Y. K. Kinetics and Mechanism of the Reduction of Iodate to Iodite by Bromide in the Presence of Phenol. J. Phys. Chem. 1971, 75, 25162522. (26) Frerichs, G. A., et al. Unpublished data. (27) Gyorgyi, L.; Turanyi, T.; Field, R. J. Mechanistic Details of the Oscillatory Belousov-Zhabotinskii Reaction. J. Phys. Chem. 1990, 94, 7162-7170. (28) Kumpinski, E.; Epstein, I. R. Effects of Temperature on Oscillatory Behavior in the Bromate-Bromide-Manganous System. J. Phys. Chem. 1985, 89, 688-692. (29) Tikhonova, L. P.; Kovalenko, A. S. Redox Interaction of Cerium(III) and Cerium(IV), or Manganese(II) and Manganese(III) Ions with Bromate and Malonic and Bromomalonic Acids. Theor. and Exp. Chemistry 1983, 19, 522528.



(30) Harris, D. Exploring Chemical Analysis; W. H. Freeman: New York, 1997. (31) Kemp, T. J.; Waters, W. A. The Oxidation of Malonic Acid by Manganic Sulfate. J. Chem. Soc. 1964, 4, 1489-1493. (32) Presented in part before the 49th Midwest Regional Meeting of the American Chemical Society at Columbia, MO, November 2014. (33) Daniels, F., et al. Exploring Physical Chemistry, 7th ed.; McGraw-Hill: New York, 1970. Figure 1. Oscillations in measured Pt potential (blue) and pH (red) for BZ system in batch at 60oC. [NaBrO3]0 = 2.00 M; [MA]0 = 0.200 M; [MnSO4]0 = 0.0600 M Figure 2. Oscillations in measured Pt potential (blue) and pH (red) for BZ system in batch at 60oC. [KBrO3]0 = 1.50 M; [MA]0 = 0.500 M; [MnSO4]0 = 0.0500 M; [NaOH]0 = 0.0100 M Figure 3. Oscillations in measured Pt potential (red) and pH (green) for BZ system in batch at room temperature. [NaBrO3]0 = 2.20 M; [MA]0 = 0.200 M; [MnSO4]0 = 0.0900 M Figure 4. Oscillations in measured Pt potential (red) and pH (green) for BZ system in batch at room temperature. [NaBrO3]0 = 2.20 M; [MA]0 = 0.550 M; [MnSO4]0 = 0.0200 M Figure 5. Calculated pH oscillations for BZ system in batch at 25oC. [BrO3-]0 = 2.20 M; [MA]0 = 0.200 M; [Mn2+]0 = 0.0900 M; [Br-]0 = .0210 M; [H+]0 = 0.0162 M. Time axis units are seconds. Figure 6. Calculated oscillations in [Br-] (spike-like peaks) and [Mn(III)BrMA+] (saw tooth-like peaks) for BZ system in batch at 25oC. [BrO3-]0 = 2.20 M; [MA]0 = 0.200 M; [Mn2+]0 = 0.0900 M; [Br-]0 = .0210 M; [H+]0 = 0.0162 M. Concentrations in moles L-1 a re shown on the vertical axes. Time axis units are seconds.


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For Table of Contents Only

Table of Contents Section

Page Number

Title Page

1

Abstract

2

Introduction

3

Rationale

4

Experimental

6



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Results

7

Discussion

8

Conclusions

11

Acknowledgment

13

Table 1

13

Table 2

15

Figure 1

16

Figure 2

17

Figure 3

18

Figure 4

19

Figure 5

20

Figure 6

21

References

22

Captions

24

TOC Graphic

25


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Batch pH Oscillations in the BelousovâZhabotinsky Reaction - The

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