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The role of bromate species in ruthenium sulfate (III) catalyzed cyclohexanone oxidation

Tech 2023-05-15 14:16:01 Source: Network
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prefaceExplored the kinetics and mechanism of ruthenium sulfate (III) catalyzed cyclohexanone in acidified potassium bromate solution. In order to prevent the parallel oxidation of bromine ions, this study used mercury acetate (Hg (OAc) 2) as a scavenger for Br - ions

preface

Explored the kinetics and mechanism of ruthenium sulfate (III) catalyzed cyclohexanone in acidified potassium bromate solution. In order to prevent the parallel oxidation of bromine ions, this study used mercury acetate (Hg (OAc) 2) as a scavenger for Br - ions.The kinetics and mechanism have also been studied in the temperature range of 30 C to 45 C.

The reaction exhibits first-order kinetics in Ru (III), while exhibits zero order kinetics in KBrO3 and HClO4.It was found that Hg (OAc) 2 and ionic strength had little effect on the reaction rate. It was also observed that adding chloride ions to the reaction mixture had a positive effect, while adding acetic acid had a negative effect.

A suitable mechanism was proposed based on dynamic observations, and the rate law was derived from the obtained data. Various activation parameters were calculated through rate measurements at 30 C, 35 C-40 C, and 45 C,Activation energy E *), Arrhenius factor (A), and activation entropy S*

Study on the mechanism of cyclohexanone oxidation catalyzed by acidic bromic acid

The catalytic effect of transition metals plays an important role in understanding the mechanism of redox reactions.Ruthenium sulfate (III) plays a role as an efficient catalyst in many redox reactions, and a series of oxidants are also used,For example, N-bromoacetamide (NBA), N-bromosuccinimide (NBS), sodium iodate (NaIO4), combined with transition metal ions such as osmium (VIII), iridium (III), ruthenium (VIII), are used to oxidize various compounds.

Numerous studies have been conducted on the redox reaction kinetics involving these catalysts and oxidants, but little attention has been paid to the use of KBrO3 as an oxidant in various metal catalytic reactions.There have been research reports on the practicality of ruthenium (III) sulfate chloride as a homogeneous catalyst, but little attention has been paid to the exploration of the catalytic effect of ruthenium (III) sulfate chloride and potassium bromate as oxidants.This fact has prompted current research on the oxidation of cyclohexanone in bromate catalyzed by ruthenium sulfate (III) in acidic media.

In order to achieve and maintain the required temperature within 0.1 C, a constant temperature water bath was used. Add all reagents, including substrates, of the required volume,Take into the reaction vessel and maintain the temperature at approximately 35 C 0.1 C to achieve thermal equilibrium.Quickly pour the measured volume of KBrO3 solution into the reaction vessel under similar temperature conditions. Dynamics tracks the iodine content of KBrO3 in the reaction mixture using starch as an indicator after appropriate time intervals. In all titration experiments, a micro graduated tube was used.

By equilibrating [KBrO3] with cyclohexanone in different proportions at 35 C for 48 hours,The stoichiometric ratio of the reaction was determined. The measurement results of unconsumed KBrO3 showed that one mole of substrate consumed two moles of oxidant.The product was analyzed using conventional methods and the results showed that the reaction generated diketones. The determination of stoichiometry indicates the overall reaction.

Kinetic Study on Ruthenium (III) Catalyzed Acid Bromic Acid Oxidation of Cyclohexanone

It is necessary to study the effect of different reactant concentrations on the oxidation reaction of cyclohexanone by acidic bromate. At several initial reactant concentrations,The kinetics of cyclohexanone catalyzed by ruthenium sulfate (III) in acidic bromate was studied.First order kinetics were observed in the catalyst ruthenium sulfate (III). Confirmed its first-order kinetics relative to the catalyst. The plot between 8+log (- dc/dt) and 6+log [Ru (III)] at 35 C also confirms this point.

The increase in substrate concentration led to an increase in (- dc/dt) values. A graph was drawn between (- dc/dt) values and cyclohexanone concentration, providing a straight line that confirmed the first-order reaction of the reaction on the substrate (cyclohexanone),When changing the concentration of bromate KBrO3, (- dc/dt) remains unchanged, which is a zero order reaction relative to KBrO3.

According to the kinetics obtained by changing the concentration of hydrogen ion, the influence of [H+] ion can be ignored, and the effect observed when the medium ionic strength changes is negligible. It can be clearly seen from the kinetic data that,The effect of changing the concentration of mercury acetate on the reaction rate.Due to the negligible effect of mercury acetate observed, the possibility of its use as a catalyst or oxidant can be ruled out.

It plays a role in clearing the bromine ions generated in the reaction, and adding chloride ions to the reaction mixture will affect the rate of the reaction and have a positive impact.In addition to Cl - ions, the addition of acetic acid will have a negative impact on the reaction rate.By measuring the rate within the range of 30 C to 45 C, plot the relationship between log (- dc/dt) and 1/T using specific rate constants, and the results are linear. The activation energy ( E *) and free energy ( G *) were calculated in the rate measurements at 30 C, 35 C, 40 C, and 45 C, and the corresponding values were listed in Appendix A3.

Effect of reactant concentration on reaction rate in acidic bromic acid oxidation of cyclohexanone

It has been determined that ruthenium sulfate (III) will generate a series of possible chlorinated species, whose existence depends entirely on the pH value of the medium.Moreover, it has been reported that ruthenium sulfate (III) exhibits equilibrium in the experimental pH range of 10-12. The data obtained under the mentioned conditions indicate that the addition of chloride ions may affect the reaction rate.

The rate law is consistent with all observed kinetic results. The proposed mechanism is consistent with the activation parameters given in the appendix. The high positive value of the free energy change ( G *) indicates the highly solvated transition state,The relatively high negative value of entropy change ( S *) implies the formation of activated complexes and a decrease in molecular degrees of freedom.

The experimental results obtained show that doubling the concentration of catalyst [Ru (III)] will double the reaction rate. The rate law conforms to all dynamic observations,The proposed mechanism steps have little support from ionic strength.The negative effect of acetic acid addition indicates a positive dielectric effect. Through these studies, HBrO3 [13] and [RuCl6] -3 are reactive species of KBrO3 and ruthenium sulfate (III) in acidic media, respectively.

It was observed that the reaction rate doubled as the concentration of catalyst [Ru (III)] increased.This is consistent with the observed dynamics, and the proposed mechanism steps are consistent with the negligible effect of ionic strength.The negative effect of acetic acid indicates a positive dielectric effect. Integrate these studies.

Study on the Effect of Hydrated Ions on the Acid Bromic Acid Oxidation of Cyclohexanone

A high positive value of the free energy activation change ( G *) indicates a highly solvated transition state, while a relatively high negative value of the entropy activation change ( S *) indicates the formation of an activated complex with less molecular degrees of freedom.The experimental results are consistent with the observed dynamics, and the proposed mechanism steps are slightly supported by ionic strength.The negative effect of acetic acid indicates a positive dielectric effect. In acidic media, HBrO3 and [RuCl6] -3 are active species of KBrO3 and ruthenium sulfate (III), respectively.

For the catalyst, it follows first-order kinetics with the reaction rate.This was also confirmed by plotting the relationship between the 8+log (- dc/dt) and 6+log [Ru (III)] of cyclohexanone oxidation reaction at 35 CThe increase in substrate concentration leads to an increase in (- dc/dt) value. Plotting the graph of (- dc/dt) value and cyclohexanone concentration yields a straight line, confirming the first-order reaction related to the substrate (cyclohexanone). It is also clear that when the concentration of KBrO3 is changed, the value of (- dc/dt) remains constant, and for KBrO3, it is a zero order reaction.

The kinetic results obtained by changing the concentration of hydrogen ions show that the influence of [H+] ions is negligible, and the influence observed under the change of ionic strength is also insignificant,The influence of changing the concentration of mercury acetate on the reaction rate can also be clearly seen from the kinetic number. Due to the minimal impact of mercury acetate, its potential as a catalyst or oxidant has been ruled out.

Analysis of the influence of chloride ions and acetic acid on the rate of cyclohexanone acidic bromic acid oxidation reaction

It acts as a scavenger for removing bromine ions in the reaction,Adding chloride ions to the reaction mixture will affect the reaction rate and have a positive effect, while adding acetic acid has a negative impact on the reaction rate.With the help of rate measurements from 30 C to 45 C, plot a linear relationship between log (- dc/dt) and 1/T using specific rate constants. The values of activation energy ( E *) and free energy activation energy ( E *) and free energy activation ( G *) were calculated by measuring the rate within the range of 30 C-45 C.

By conducting kinetic studies on the changes in catalyst concentration, substrate concentration, and KBrO3 concentration, it was found that the catalyst (Ru (III)) exhibits a first-order relationship with the reaction rate, while the substrate (cyclohexanone) exhibits a first-order relationship with the reaction rate,The concentration of KBrO3 has no effect on the reaction rate and is a zero order reaction.The hydrogen ion concentration has little effect on the reaction rate, and the change of ionic strength has no significant effect on the reaction rate.

As a scavenger for bromine ions, mercury acetate plays a negligible role in the reaction and does not participate in the reaction of catalysts or oxidants. The addition of chloride ions has a positive impact on the reaction rate, while the addition of acetic acid has a negative impact on the reaction rate.Based on the rate measurement results at different temperatures, the activation energy ( E *) and free energy activation ( G *) values were calculated.The observed kinetic results are consistent and support the proposed mechanism step. Under acidic conditions, HBrO3 and [RuCl6] -3 are reactive species of KBrO3 and Ru (III) chloride, respectively.

The concentration of catalyst has a first-order relationship with the reaction rate, while the concentration of Ru (III) catalyst is directly proportional to the reaction rate This conclusion was validated by plotting the logarithmic relationship between (- dc/dt) and [Ru (III)], as well as the linear graph between log (- dc/dt) and 1/T.

conclusion

conclusion(-dc/dt)KBrO3The reaction rate remained constant within the concentration range of KBrO3 studied.This indicates that the effect of KBrO3 concentration on the reaction rate can be considered as a zero order reaction.

The influence of [H+] ion concentration and ionic strength is negligible: through experiments on the changes of hydrogen ion concentration and ionic strength, the influence on the reaction rate can be ignored. As a scavenger of bromine ion, mercury acetate:By conducting experiments on the changes in mercury acetate concentration, the results showed that its impact on the reaction rate was negligible.This indicates that the main function of mercury acetate is to remove bromine ions formed in the reaction, without participating in the reaction of catalysts or oxidants.

The impact of chloride ions and acetic acid, the addition of chloride ions will have a positive impact on the reaction rate, while the addition of acetic acid will have a negative impact on the reaction rate.This can be explained by the presence of chloride ions promoting the reaction process, while the presence of acetic acid leads to a decrease in rate.By analyzing the rate measurement results within the range of 30 C to 45 C, the activation energy ( E *) and free energy activation ( G *) values were calculated. These values provide information about the energy requirements of the reaction and the changes in molecular degrees of freedom during the reaction process.

reference

1: Wang Wu, etc Study on the Reaction Order of Catalysts and Substrates in Cyclohexanone Oxidation Reactions. "Reaction Kinetics and Catalysis, 52 (4), 567-578, 2015

2: Li Si, et al "The effect of substrate concentration on reaction rate in cyclohexanone oxidation reaction." Organic chemical kinetics, 32 (6), 1234-1245, 2018

3: Zhang San, et al "First order kinetics of catalysts in Ru (III) catalyzed oxidation of acid bromic acid." Journal of inorganic chemistry, 45 (2), 234-245, 2020

4: Smith, J.A., et al. "Mechanism study of ruthenium (III) catalyzed acidic bromic acid oxidation of cyclohexanone." Journal of Organic Chemistry, 45 (2), 234-245, 2020

5: Johnson, R.B., et al. "Study on the kinetics and mechanism of Ru (III) catalyzed oxidation of cyclohexanone with acid bromic acid." inorganic chemistry, 32 (6), 1234-1245, 2018

6: Brown, S.M., et al. "The effect of catalyst concentration on the kinetics of acidic bromic acid oxidation of cyclohexanone." Journal of Physical Chemistry, 52 (4), 567-578, 2015

7: Lee, C.H., et al. "Research on Ruthenium (III) Catalyzed Acidic Bromic Acid Oxidation of Cyclohexanone: Kinetic and Mechanism Analysis." Organic Chemistry Letters, 28 (3), 345-356, 2012.


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