Kinetics and Mechanism of the Catalysis of the Decomposition of Hydrogen Peroxide by Schiff Base Complexes of Copper(II) PDF Download
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Author: Timothy Kum Beng
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Languages : en
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Spectroscopic studies have been used to describe the mechanism of the decomposition of hydrogen peroxide by solutions of a dimeric Cu(II) complex of a dissymetric Schiff base, [CuSALAD]2.H2O, and imidazole or methyl substituted imidazoles, B, which form monomeric CuSALADB2 complexes, in aqueous ethanol solvent. Freezing Point Depression and Vapor Pressure Lowering studies were carried out to confirm the dimeric nature of the [CuSALAD]2.H2O complex that had been previously reported. The stoichiometry of the [CuSALAD] .H O-imidazole equilibrium was extensively studied pointing to a 1:4 stoichiometry. The CuSALAD. B2 adducts exhibited certain catalytic properties that mimic those of catalase enzymes. The different imidazoles were buffered to acidic, neutral and basic pH media in order to investigate the pH effects of this reaction. Two charge transfer (CT) bands were observed near 420 and 450 nm upon addition of hydrogen peroxide to CuSALADB2 solutions, and were associated with two proposed intermediates (CuBOOH and CuBOOCu). A mechanism consistent with these results has been developed. First order dependence of the rate on CuSALAD. B2 was observed in the presence of excess CuSALAD. B2 over hydrogen peroxide whereas second order dependence was observed with the latter in excess. The CuBOOCu intermediate was unstable in the presence of EDTA and a first order dependence of rate of formation of intermediate on both CuSALAD. B2, and hydrogen peroxide was observed.
Author: Timothy Kum Beng
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Languages : en
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Book Description
Spectroscopic studies have been used to describe the mechanism of the decomposition of hydrogen peroxide by solutions of a dimeric Cu(II) complex of a dissymetric Schiff base, [CuSALAD]2.H2O, and imidazole or methyl substituted imidazoles, B, which form monomeric CuSALADB2 complexes, in aqueous ethanol solvent. Freezing Point Depression and Vapor Pressure Lowering studies were carried out to confirm the dimeric nature of the [CuSALAD]2.H2O complex that had been previously reported. The stoichiometry of the [CuSALAD] .H O-imidazole equilibrium was extensively studied pointing to a 1:4 stoichiometry. The CuSALAD. B2 adducts exhibited certain catalytic properties that mimic those of catalase enzymes. The different imidazoles were buffered to acidic, neutral and basic pH media in order to investigate the pH effects of this reaction. Two charge transfer (CT) bands were observed near 420 and 450 nm upon addition of hydrogen peroxide to CuSALADB2 solutions, and were associated with two proposed intermediates (CuBOOH and CuBOOCu). A mechanism consistent with these results has been developed. First order dependence of the rate on CuSALAD. B2 was observed in the presence of excess CuSALAD. B2 over hydrogen peroxide whereas second order dependence was observed with the latter in excess. The CuBOOCu intermediate was unstable in the presence of EDTA and a first order dependence of rate of formation of intermediate on both CuSALAD. B2, and hydrogen peroxide was observed.
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Languages : en
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Book Description
Spectroscopic studies have been used to describe the mechanism of the decomposition of hydrogen peroxide by solutions of a dimeric Cu(II) complex of a dissymetric Schiff base, [CuSALAD]2.H2O, and imidazole or methyl substituted imidazoles, B, which form monomeric CuSALADB2 complexes, in aqueous ethanol solvent. Freezing Point Depression and Vapor Pressure Lowering studies were carried out to confirm the dimeric nature of the [CuSALAD]2.H2O complex that had been previously reported. The stoichiometry of the [CuSALAD]2.H2O-imidazole equilibrium was extensively studied pointing to a 1:4 stoichiometry. The CuSALAD. B2 adducts exhibited certain catalytic properties that mimic those of catalase enzymes. The different imidazoles were buffered to acidic, neutral and basic pH media in order to investigate the pH effects of this reaction. Two charge transfer (CT) bands were observed near 420 and 450 nm upon addition of hydrogen peroxide to CuSALADB2 solutions, and were associated with two proposed intermediates (CuBOOH and CuBOOCu). A mechanism consistent with these results has been developed. First order dependence of the rate on CuSALAD. B2 was observed in the presence of excess CuSALAD. B2 over hydrogen peroxide whereas second order dependence was observed with the latter in excess. The CuBOOCu intermediate was unstable in the presence of EDTA and a first order dependence of rate of formation of intermediate on both CuSALAD. B2, and hydrogen peroxide was observed.
Author: John D. Davis
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Languages : en
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Previous studies involving copper (II) complexed with a dissymmetric Schiff base and imidazole derivatives had identified catalase activity of these complexes towards H O . Reactions such as this are of great interest due to the important role of copper-based complexes in biological systems. Our research has been conducted to add to the base of knowledge regarding the efforts of other researchers to investigate copper complexes that exhibit similar reactivity as copper-based proteins towards dioxygen. The copper complex chosen for this study contained a tri-dentate Schiff base adduct which, when complexed with an imidazole derivative, limited the manner in which peroxo adducts could bind while providing distinct spectral peaks which were used to conduct kinetic studies. Our results indicate a reaction mechanism by which the role of the complexed copper (II) ion is to activate the peroxo adduct for decomposition through reactions with other peroxide molecules, dioxygen, and water.
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Languages : en
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Previous studies involving copper (II) complexed with a dissymmetric Schiff base and imidazole derivatives had identified catalase activity of these complexes towards H2O2. Reactions such as this are of great interest due to the important role of copper-based complexes in biological systems. Our research has been conducted to add to the base of knowledge regarding the efforts of other researchers to investigate copper complexes that exhibit similar reactivity as copper-based proteins towards dioxygen. The copper complex chosen for this study contained a tri-dentate Schiff base adduct which, when complexed with an imidazole derivative, limited the manner in which peroxo adducts could bind while providing distinct spectral peaks which were used to conduct kinetic studies. Our results indicate a reaction mechanism by which the role of the complexed copper (II) ion is to activate the peroxo adduct for decomposition through reactions with other peroxide molecules, dioxygen, and water.
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Category :
Languages : en
Pages : 70
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Book Description
Catalysis is a very interesting area of chemistry, which is currently developing at a rapid pace. A great deal of effort is being put forth by both industry and academia to make reactions faster and more productive. One method of accomplishing this is by the development of catalysts. Enzymes are an example of catalysts that are able to perform reactions on a very rapid time scale and also very specifically; a goal for every man-made catalyst. A kinetic study can also be carried out for a reaction to gain a better understanding of its mechanism and to determine what type of catalyst would assist the reaction. Kinetic studies can also help determine other factors, such as the shelf life of a chemical, or the optimum temperature for an industrial scale reaction. An area of catalysis being studied at this time is that of oxygenations. Life on this earth depends on the kinetic barriers for oxygen in its various forms. If it were not for these barriers, molecular oxygen, water, and the oxygenated materials in the land would be in a constant equilibrium. These same barriers must be overcome when performing oxygenation reactions on the laboratory or industrial scale. By performing kinetic studies and developing catalysts for these reactions, a large number of reactions can be made more economical, while making less unwanted byproducts. For this dissertation the activation by transition metal complexes of hydrogen peroxide or molecular oxygen coordination will be discussed.
Author:
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Category : Chemistry, Physical and theoretical
Languages : en
Pages : 630
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Author: M.V. Twigg
Publisher: Springer Science & Business Media
ISBN: 1489916245
Category : Science
Languages : en
Pages : 504
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Book Description
Mechanisms of Inorganic and Organometallic Reactions provides an ongoing critical review of the primary literature concerned with mechanisms of inorganic and organometallic reactions. The main focus is on reactions in solution, although solid-state and gas-phase studies are included where they provide relevant mechanistic insight. Each volume covers an eighteen-month literature period, and this, the eighth volume in the series, includes papers published during January 1990 through June 1991. Where appropriate, references to earlier reports and to specific sections in previous volumes are given. Coverage spans the whole area as comprehensively as possible in each volume, and while it is impossible to be absolutely exhaustive, every effort is made to include all of the important published work that is relevant to the elucidation of reaction mechanisms. Numerical data are reported in the units used by the original authors, and they are converted to common units only when comparisons are being made. The successful format of earlier volumes is retained to facilitate tracing progress over several years in a particular topic, and the series now permits this to be done for a twelve-year period. The introduction three volumes ago of computerized techniques to improve cross-referencing in the Index brought positive reader comments, and their use is being continued.
Author: G. Strukul
Publisher: Springer Science & Business Media
ISBN: 940170984X
Category : Science
Languages : en
Pages : 287
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Book Description
Hydrogen peroxide is a chemical that is becoming increasingly fashionable as an oxidant, both in industry and in academia and whose production is expected to increase significantly in the next few years. This growth in interest is largely due to environmental considerations related to the clean nature of hydrogen peroxide as an oxidant, its by-product being only water. To date this chemical has largely been employed as a non-selective oxidant in operations like the bleaching of paper, cellulose and textiles, or in the formulation of detergents, and only to a minimal extent in the manufacture of organic chemicals. This book has been organized to cover the different aspects of the chemistry of hydrogen peroxide. The various chapters into which the book is divided have been written critically by the authors with the general aim of stimulating new ideas and emphasizing those aspects that are likely to lead to new developments in organic synthesis in the coming future.
Author:
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Category : Analytical chemistry
Languages : en
Pages : 648
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Author: Van Lorens Bohnson
Publisher:
ISBN:
Category : Hydrogen peroxide
Languages : en
Pages : 78
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