Factors affecting oxidation rate

The extreme sensitivity of oxazaphosphorinanes is surprising and shows that there can be discrepancies between basicity and oxygen sensitivity, pointing out that factors affecting oxidation rates in tricoordinated phosphorus compounds are still not clearly understood. 

The objective of this study was to document changes in Cu-Zn tailings during one year of exposure to oxidizing conditions. The primary factor affecting the rate of tailings acidification is the primary mineralogy. 

A similar phenomenon can be observed in the cuffs and balloons of tracheal tubes, flotation catheters, etc. Increases in cuff pressure may be sufficient to cause mucosal ischaemia with subsequent damage to the tracheal mucosa. In the case of pulmonary flotation catheters, there is a risk of cuff rupture followed by gas embolism and infarction. A number of factors affect the rate of volume and pressure change—time, permeability, elasticity, initial volume and pressure, nitrous oxide concentration, temperature. 

ScholesG, Willson RL, Ebert M (1969) Pulse radiolysis of agueous solutions of deoxyribonudeotides and of DNA reaction with hydroxy-radicals. Chem Commun 17-18 Schuchmann MN, von Sonntag C (1982) Flydroxyl radical induced oxidation of diethyl ether in oxygenated aqueous solution. A product and pulse radiolysis study. J PhysChem 86 1995-2000 Shragge PC, Michaels FIB, Flunt JW (1971) Factors affecting the rate of hydrated electron attack on polynucleotides. Radiat Res 47 598-611... 

The factors affecting the rates of sorption and desorption of the heavy metals by the hydrous oxides. 

Lipid oxidation is responsible for rancidity, development of off-fiavors, and the loss of fat-soluble vitamins and pigments in many foods, espedaUy in dehydrated foods. Factors which affect oxidation rate include moisture content, type of substrate (fatty acid), extent of reaction, oxygen content, tanperature, presence of metals, presence of natural antioxidants, enzyme activity, UV light, protein content, free amino... 

Phosphine, Amines and Alkenes as Factors Affecting the Rate of the Oxidative Addition. Amatore, Jutand et al. [29] have established that excess PPhs slows down the oxidative addition by formation of the nonreactive Pd°(PPh3)3(OAc)", thereby decreasing the concentration of the reactive Pd°(PPh3)2(OAc) by equilibrium with Pd°(PPh3)3(OAc) . 

A number of other reactions have been demonstrated in which an oxidative transformation occurs at an interface, but the factors affecting the rates have not been examined [2]. Some progress in this direction was made in a simple redox reaction between hydro-phobic porphyrin dissolved in octane and a hydrophilic donor - sodium dithionite dissolved in water [43]. 

Amines and Alkenes as Factors Affecting the Rates of Both the Oxidative Addition and Carbopalladation The base (NEt ) plays a multiple role. It stabilizes Pd (PPh3)2(OAc) versus its decomposition to Pd"(PPh3)2 by protons and consequently slows down the oxidative addition (Scheme 19.7) [7c, 1, p]. The base accelerates the overall carbopalladation by shifting the equilibrium toward PhPd(OAc)L2 upon quenching the proton (Scheme 19.9) [71]. It favors the recycling of the Pd complex from the hydrido-Pd . The formation of HPd PPhj) was proposed by Heck (Scheme 19.2). In DMF, the cationic [HPd(PPh3)2S] must be formed with acetate as the counter anion (Amatore/Jutand [7m]). 

The erosion of graphite in nozzle appHcations is a result of both chemical and mechanical factors. Changes in temperature, pressure, or fuel-oxidizing ratio markedly affect erosion rates. Graphite properties affecting its resistance to erosion include density, porosity, and pore size distribution... 

The calciothermic reduction of an oxide is naturally designed for the obtainment of the reduced metal in the powder form because of the high melting point of the other product, namely, calcia. The formation of the metal in the form of a powder is favored by some other controllable factors also. One of these factors is that the temperature should not exceed the melting point of the metal during reduction. A second factor is that it is preferable to have the reaction temperature as low as possible, without adversely affecting the rate of the reaction. 

First, the rate of heat production is again related to the sum of the rates of depositional and burning processes, and if the predominant factor affecting the overall rate is temperature, then it does not seem likely that the specific effect of water vapor on the oxidation reported here is chemical catalysis, since a lowering of activation energy for either process would result in an increase in the overall rate relative to dry oxidation. 

Injection of air the oxygen in the injected air will prevent sulfate-reducing conditions in the sewer. The DO concentration in the wastewater establishes an aerobic upper layer in the biofilm, and sulfide produced in the deeper part of the biofilm or the deposits that may diffuse into the water phase will be oxidized (cf. Figure 6.2). The oxidation of sulfide will mainly proceed as a chemical process, although microbial oxidation may also take place (Chen and Morris, 1972). Factors that affect the oxidation rate of sulfide include pH, temperature and presence of catalysts, e.g., heavy metals. 

Mn(II) oxidation is enhanced in the presence of lepidocrocite (y-FeOOH). The oxidation of Mn(II) on y-FeOOH can be understood in terms of the coupling of surface coordination processes and redox reactions on the surface. Ca2+, Mg2+, Cl, S042-, phosphate, silicate, salicylate, and phthalate affect Mn(II) oxidation in the presence of y-FeOOH. These effects can be explained in terms of the influence these ions have on the binding of Mn(II) species to the surface. Extrapolation of the laboratory results to the conditions prevailing in natural waters predicts that the factors which most influence Mn(II) oxidation rates are pH, temperature, the amount of surface, ionic strength, and Mg2+ and Cl" concentrations. 

The theory of premixed flames essentially consists of an analysis of factors such as mass diffusion, heat diffusion, and the reaction mechanisms as they affect the rate of homogeneous reactions taking place. Inasmuch as the primary mixing processes of fuel and oxidizer appear to dominate the burning processes in diffusion flames, the theories emphasize the rates of mixing (diffusion) in deriving the characteristics of such flames. 

Some substrates show limited solubility in sulfuric acid solutions and this can affect the rate of oxidation. However, the main factor for slow amine oxidation is due to the high concentration of protonated amine under these highly acidic conditions. Under these conditions only weakly basic amines have a high enough concentration of unprotonated form to permit oxidation to occur. As a result, sulfuric acid solutions of peroxydisulfuric acid are only useful for the oxidation of very weakly basic amines. Peroxydisulfuric acid oxidizes trinitrotoluidines to tetranitrotoluenes (Table4.1, Entry 3) but leaves the more basic dinitrotoluidines unaffected. The opposite is true of peroxyacids like peroxytrifluoroacetic acid and so the reagents are very much complementary. 

Reactivity ratios for all the combinations of butadiene, styrene, Tetralin, and cumene give consistent sets of reactivities for these hydrocarbons in the approximate ratios 30 14 5.5 1 at 50°C. These ratios are nearly independent of the alkyl-peroxy radical involved. Co-oxidations of Tetralin-Decalin mixtures show that steric effects can affect relative reactivities of hydrocarbons by a factor up to 2. Polar effects of similar magnitude may arise when hydrocarbons are cooxidized with other organic compounds. Many of the previously published reactivity ratios appear to be subject to considerable experimental errors. Large abnormalities in oxidation rates of hydrocarbon mixtures are expected with only a few hydrocarbons in which reaction is confined to tertiary carbon-hydrogen bonds. Several measures of relative reactivities of hydrocarbons in oxidations are compared. 

The incremental reactivity of a VOC is the product of two fundamental factors, its kinetic reactivity and its mechanistic reactivity. The former reflects its rate of reaction, particularly with the OH radical, which, as we have seen, with some important exceptions (ozonolysis and photolysis of certain VOCs) initiates most atmospheric oxidations. Table 16.8, for example, also shows the rate constants for reaction of CO and the individual VOC with OH at 298 K. For many compounds, e.g., propene vs ethane, the faster the initial attack of OH on the VOC, the greater the IR. However, the second factor, reflecting the oxidation mechanism, can be determining in some cases as, for example, discussed earlier for benzaldehyde. For a detailed discussion of the factors affecting kinetic and mechanistic reactivities, based on environmental chamber measurements combined with modeling, see Carter et al. (1995) and Carter (1995). 

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