Catalysis hydrogen peroxide, decomposition

The mechanism and rate of hydrogen peroxide decomposition depend on many factors, including temperature, pH, presence or absence of a catalyst (7—10), such as metal ions, oxides, and hydroxides etc. Some common metal ions that actively support homogeneous catalysis of the decomposition include ferrous, ferric, cuprous, cupric, chromate, dichromate, molybdate, tungstate, and vanadate. For combinations, such as iron and... 

Metal-ion catalysis of hydrogen peroxide decomposition can generate perhydroxyl and hydroxyl free radicals as in Scheme 10.26 [235]. The catalytic effects of Fe2+ and Fe3+ ions are found to be similar [235]. It is not necessary for the active catalyst to be dissolved [237], as rust particles can be a prime cause of local damage. The degradative free-radical reaction competes with the bleaching reaction, as illustrated in Scheme 10.27 [237]. Two adverse consequences arise from the presence of free radicals ... 

The catalysis of hydrogen peroxide decomposition by iron ions occupies a special place in redox catalysis. This was precisely the reaction for which the concept of redox cyclic reactions as the basis for this type of catalysis was formulated [10-13]. The detailed study of the steps of this process provided a series of valuable data on the mechanism of redox catalysis [14-17]. The catalytic decomposition of H202 is an important reaction in the system of processes that occur in the organism [18-22]. 

The most numerous cases of homogeneous catalysis are by certain ions or metal coordination compounds in aqueous solution and in biochemistry, where enzymes function catalytically. Many ionic effects are known. The hydronium ion H3O and the hydroxyl ion OH catalyze hydrolyses such as those of esters ferrous ion catalyzes the decomposition of hydrogen peroxide decomposition of nitramide is catalyzed by acetate ion. Other instances are inversion of sucrose by HCl, halogenation of acetone by H and OH , hydration of isobutene by acids, hydrolysis of esters by acids, and others. 

In the section 2.3. we presented catalysis by complexes of transition metals and argued that this type of homogeneous catalysis is gaining importance in industrial processes. Kinetic models of several reactions will be considered in the next paragraph. Here we would like to address reactions where the metal ions act as catalysts. As an example of such a process, hydrogen peroxide decomposition will be considered. Transition metals, mainly manganese, iron and copper, are effcient catalysts for this reaction. 

The first chapter of the book deals with enzyme-like eatalysis by synthetic polymers - catalysis by polymeric acids and bases, amphoteric polyelectrolytes and nonionic polymers. Because coordination compounds of metal ions with macromolecular ligands are interesting with regard to bioinorganic chemistry, this book elucidates some problems involving the catalysis by water-soluble polymer-metal complexes. Ester hydrolysis, hydrogen peroxide decomposition, oxidation of disubstituted phenols, hydroquinones, mercaptoalcohols and other types of reaction are chosen as model processes. A section devoted to interfacial catalysis is also included. 

A FIGURE 14.22 Homogeneous catalysis. Effect of catalyst on the speed of hydrogen peroxide decomposition to water and oxygen gas. 

This method is highly advantageous in that it gives highly reproducible results, the reagents are readily available, inexpensive and stable for long durations. In addition, possible metal ion catalysis of hydrogen peroxide decomposition would not interfere with the overall stoichiometry of the system. 

Hasan, M.A., Zaki, M.I., Pasupulety, L and Kumari, K. (1999) Promotion of the hydrogen peroxide decomposition activity of manganese oxide catalysts. Applied Catalysis A, 181,171-9. 

Catalysis of hydrogen peroxide decomposition by iron ions... 

Enzyme catalysis. An enzyme in the potato is catalyzing the decomposition of a hydrogen peroxide solution, as shown by the bubbles of oxygen. 

An example of a reaction that is subject to homogeneous catalysis is the decomposition of hydrogen peroxide in aqueous solution ... 

It gives rise to an extremely violent reaction with hydrogen peroxide. This is certainly due to the catalysis of the decomposition of peroxide caused by the phosphoric acid produced by water. 

In contact with fluorine, when it is cold, nickel oxide glows. It reacts violently with hydrogen peroxide (catalysis of its decomposition ). Finally, in contact with a mixture of hydrogen sulphide and air, it glows and causes this gaseous mixture to detonate. 

The violent decomposition observed on adding charcoal to cone, hydrogen peroxide is mainly owing to catalysis by metallic impurities present and the active surface of the charcoal, rather than to direct oxidation of the carbon [1], Charcoal mixed with a trace of manganese dioxide ignites immediately on contact with cone, peroxide [2],... 

Concerning the mode of formation of ES, we prefer the concept that the substrate in a monolayer is chemisorbed to the active center of the enzyme protein, just as the experimental evidence pertaining to surface catalysis by inorganic catalysts indicates that in these reactions chemisorbed, not physically adsorbed, reactants are involved. Such a concept is supported by the demonstration of spectroscopically defined unstable intermediate compounds between enzyme and substrate in the decomposition by catalase of ethyl hydroperoxide,11 and in the interaction between peroxidase and hydrogen peroxide.18 Recently Chance18 determined by direct photoelectric measurements the dissociation con-... 

Similar results were obtained for tert-butyl hydroperoxide and perchloric acid in 2-propanol. Thus, it is evident from the decomposition of hydrogen peroxide into free radicals that both heterolytic and homolytic reactions may be catalyzed by hydrogen ions. Further research is needed to investigate proton catalysis in certain homolytic reactions. 

Catalytic Decomposition of Hydrogen Peroxide by Ferrous Ions Catalysis by Transition Metal Ions and Complexes in Liquid-Phase Oxidation of Hydrocarbons and Aldehydes by Dioxygen... 

Dowden and Reynolds observed that the rates of decomposition of hydrogen peroxide decreased from pure copper to copper-nickel alloys, thus suggesting that negative ion formation takes place in the heterogeneous catalytic reaction, in agreement with the Haber and Weiss mechanism based on catalysis in solution. 

In the same year Jacob Berzelius introduced the concept of catalysis, which he developed as a result of studies of the effects of acids and bases in promoting the hydrolysis of starch and of the effects of metals on the decomposition of hydrogen peroxide. Berzelius proposed the term catalyst from the Greek "katalysis," meaning "dissolution." Although he had been concerned primarily with inorganic catalysts, Berzelius recognized that a natural catalyst,... 

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