Hydrogen peroxide reaction rate

In principle there is a competition for the HO2 radical between peroxydisulphate and hydrogen peroxide [reactions (63) and (86)] however, when the stoichiometry is 1 1 reaction (86) can be neglected. Assuming that the chain length is large, with the usual steady-state approximation, we obtain the following rate equation ... 

Similarly to Mb, Hb is also active in the catalytic oxidation of substrates by hydrogen peroxide, with rates and general behavior comparable with those of Mb. In particular, a number of research reports showed that Hb exhibits oxidizing activities and can be used as a mimetic peroxidase to catalyze the oxidation reactions of aromatic compounds [180-182], aniline [183, 184], lipids [185], styrene [186], and sulfides [187]. Again, although the activity of Hb is not comparable with... 

It will often be necessary to avoid sulfone formation, and this can be achieved by carrying out the reaction below 50 °C, and using only stoichiometric amounts of hydrogen peroxide.373 For example, 1,4-dithiane can be selectively converted to the mono- and bis-sulfoxide by proper control over the hydrogen peroxide addition rate.374 Azeotropic removal of water by the addition of suitable solvents can also increase selectivity.375 However, if sulfones are required, then elevated temperatures should be used.376... 

The rate of film oxidation is set by the rate determining step in the cascade reaction sequence. For this system, we have observed that the film oxidation rate essentially follows the hydrogen peroxide generation rate. We can use equations (18.14) and (18.15) for iire [IJ ]o 1 to relate the triiodide flux to the triiodide generation rate and, by equation (18.10), to the bound conjugate so that... 

This reaction is slow in acidic solution, and G(H20 = Ga,Oa is found. However, in neutral and alkaline solution the rate can be appreciable and the reaction must be allowed for. It has been shown that the reaction involves a nucleophilic attack of the thiolate ion on hydrogen peroxide, the rate being found proportional to IRS ] in studies on cysteamine and cysteine in which pH was varied. 

For the decomposition of hydrogen peroxide reaction studied by Nyquist and Ramirez (1971), a second control variable is possible. This is the flow rate of potassium iodide catalyst solution to the reactor. Modify the process model to allow for a variable catalyst flow rate and therefore a variable catalyst concentration. The reaction rate is modeled as... 

Another critical parameter for safe processing is the hydrogen peroxide addition rate, which in turn depends on the reaction temperature. Hydrogen peroxide should be added at such a rate that the latter equals the rate of its consumption, thus maintaining a low stationary concentration. The rate of hydrogen peroxide consumption via the molybdate catalysed disproportionation reaches its maximum when the predominant peroxomolybdate species in solution equals the triperoxo-molybdate Mo(02)3 Since the prevalent peroxomolybdate species that is... 

Substitution and oxidation can often both be involved in reactions of tris(diimine)-iron(II) complexes with oxidizing agents. Thus, for example, reaction with hydrogen peroxide involves rate-determining dissociation as the first step. Similarly, initial dissociation seems to be the first step in the predominant pathway for superoxide oxidation of the [Fe(phen)3] cation. Dissociation may also be involved in reactions of diimine-iron(II) complexes with nitrous acid. Here and elsewhere it is recognized that these complexes react with nitric acid—in the initial stages aquation may be the only important path, but autocatalytic redox processes usually become dominant before aquation is complete, especially for the more easily oxidizable ligands and complexes. ... 

Mn(III)TMPyP is a manganese porphyrin that acts as a superoxide dismutase (SOD) mimetic and peroxynitrite decomposition catalyst (Han et al., 2001). SOD mimetics described to date are unstable and are capable of catalyzing undesired side reactions in addition to the dismutation of the superoxide radical. Mn(III)TMPyP is an SOD mimetic with increased stability to pH and hydrogen peroxide. The rate constants for superoxide dismutation and peroxynitrite decomposition are 3.9 X 10 M s and... 

Figure ll-G-l. Arrhenius plot of the rate coefficients for the OH + hydrogen peroxide reaction. 

In a 500 ml. three-necked flask, equipped with a mechanical stirrer, thermometer and dropping funnel, place 300 ml. of 88-90 per cent, formic acid and add 70 ml. of 30 per cent, hydrogen peroxide. Then introduce slowly 41 g. (51 ml.) of freshly distilled cyclohexene (Section 111,12) over a period of 20-30 minutes maintain the temperature of the reaction mixture between 40° and 45° by cooling with an ice bath and controlling the rate of addition. Keep the reaction mixture at 40° for 1 hour after all the cyclohexene has been added and then allow to stand overnight at room temperature. Remove most of the formic acid and water by distillation from a water bath under reduced pressure. Add an ice-cold solution of 40 g. of sodium hydroxide in 75 ml. of water in small portions to the residual mixture of the diol and its formate take care that the tempera... 

The earliest examples of analytical methods based on chemical kinetics, which date from the late nineteenth century, took advantage of the catalytic activity of enzymes. Typically, the enzyme was added to a solution containing a suitable substrate, and the reaction between the two was monitored for a fixed time. The enzyme s activity was determined by measuring the amount of substrate that had reacted. Enzymes also were used in procedures for the quantitative analysis of hydrogen peroxide and carbohydrates. The application of catalytic reactions continued in the first half of the twentieth century, and developments included the use of nonenzymatic catalysts, noncatalytic reactions, and differences in reaction rates when analyzing samples with several analytes. 

As the temperature is increased through the NTC zone, the contribution of alkylperoxy radicals falls. Littie alkyl hydroperoxide is made and hydrogen peroxide decomposition makes a greater contribution to radical generation. Eventually the rate goes through a minimum. At this point, reaction 2 is highly displaced to the left and alkyl radicals are the dominant radical species. 

Oxidation. Hydrogen peroxide is a strong oxidant. Most of its uses and those of its derivatives depend on this property. Hydrogen peroxide oxidizes a wide variety of organic and inorganic compounds, ranging from iodide ions to the various color bodies of unknown stmcture in ceUulosic fibers. The rate of these reactions may be quite slow or so fast that the reaction occurs on a reactive shock wave. The mechanisms of these reactions are varied and dependent on the reductive substrate, the reaction environment, and catalysis. Specific reactions are discussed in a number of general and other references (4,5,32—35). 

Because the reaction takes place in the Hquid, the amount of Hquid held in the contacting vessel is important, as are the Hquid physical properties such as viscosity, density, and surface tension. These properties affect gas bubble size and therefore phase boundary area and diffusion properties for rate considerations. Chemically, the oxidation rate is also dependent on the concentration of the anthrahydroquinone, the actual oxygen concentration in the Hquid, and the system temperature (64). The oxidation reaction is also exothermic, releasing the remaining 45% of the heat of formation from the elements. Temperature can be controUed by the various options described under hydrogenation. Added heat release can result from decomposition of hydrogen peroxide or direct reaction of H2O2 and hydroquinone (HQ) at a catalytic site (eq. 19). 

The first detailed investigation of the reaction kinetics was reported in 1984 (68). The reaction of bis(pentachlorophenyl) oxalate [1173-75-7] (PCPO) and hydrogen peroxide cataly2ed by sodium saUcylate in chlorobenzene produced chemiluminescence from diphenylamine (DPA) as a simple time—intensity profile from which a chemiluminescence decay rate constant could be determined. These studies demonstrated a first-order dependence for both PCPO and hydrogen peroxide and a zero-order dependence on the fluorescer in accord with an earher study (9). Furthermore, the chemiluminescence quantum efficiencies Qc) are dependent on the ease of oxidation of the fluorescer, an unstable, short-hved intermediate (r = 0.5 /is) serves as the chemical activator, and such a short-hved species "is not consistent with attempts to identify a relatively stable dioxetane as the intermediate" (68). 

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