Oxidation mechanism comparison

Ressler et al. (2002) XAS Mo02 Oxidation mechanism comparison to Mo03 + + + Propene oxidation... 

Thermal Oxidative Stability. ABS undergoes autoxidation and the kinetic features of the oxygen consumption reaction are consistent with an autocatalytic free-radical chain mechanism. Comparisons of the rate of oxidation of ABS with that of polybutadiene and styrene—acrylonitrile copolymer indicate that the polybutadiene component is significantly more sensitive to oxidation than the thermoplastic component (31—33). Oxidation of polybutadiene under these conditions results in embrittlement of the mbber because of cross-linking such embrittlement of the elastomer in ABS results in the loss of impact resistance. Studies have also indicated that oxidation causes detachment of the grafted styrene—acrylonitrile copolymer from the elastomer which contributes to impact deterioration (34). 

In a polluted or urban atmosphere, O formation by the CH oxidation mechanism is overshadowed by the oxidation of other VOCs. Seed OH can be produced from reactions 4 and 5, but the photodisassociation of carbonyls and nitrous acid [7782-77-6] HNO2, (formed from the reaction of OH + NO and other reactions) are also important sources of OH ia polluted environments. An imperfect, but useful, measure of the rate of O formation by VOC oxidation is the rate of the initial OH-VOC reaction, shown ia Table 4 relative to the OH-CH rate for some commonly occurring VOCs. Also given are the median VOC concentrations. Shown for comparison are the relative reaction rates for two VOC species that are emitted by vegetation isoprene and a-piuene. In general, internally bonded olefins are the most reactive, followed ia decreasiag order by terminally bonded olefins, multi alkyl aromatics, monoalkyl aromatics, C and higher paraffins, C2—C paraffins, benzene, acetylene, and ethane. 

The expected oxidation mechanisms of carbides and silicides can be analysed from a thermodynamic viewpoint by a comparison of the relative stabilities... 

The production of ozone in power-plant plumes has been suggested to explain ozone spatial distributions in nonurban areas.Comparison of oxidation mechanisms competing for sulfur dioxide suggests that three reactions—... 

In summary, the uncatalyzed oxidation of S(IV) occurs in aqueous solution but is very slow. However, given the ubiquitous occurrence of Fe3+ and Mn2+ (see Chapter 9), the uncatalyzed oxidation is likely irrelevant to atmospheric solutions. The catalyzed oxidations are complex in both kinetics and mechanism. We shall defer a comparison of their importance until other oxidation mechanisms are discussed. However, we shall see that the catalyzed oxidations are likely to contribute significantly to S(IV) oxidation in solution only at pH values near neutral, i.e., in the range of 6-7. As the oxidation occurs and acid forms, the pH falls. The rapid falloff in the rate of the catalyzed oxidation with increasing [H + ] then results in a rapid quenching of this path, as expected from Fig. 8.9a. 

It is apparent that the fate of the H atom (radical) is crucial in determining the rate of the H2-O2 reaction or, for that matter, the rate of any hydrocarbon oxidation mechanism. From the data in Appendix B one observes that at temperatures encountered in flames the rates of reaction between H atoms and many hydrocarbon species are considerably larger than the rate of the chain branching reaction (17). Note the comparisons in Table 1. Thus, these reactions compete very effectively with reaction (17) for H atoms and reduce the chain branching rate. For this reason. 

Guengerich FP, Yun CH, Macdonald TL. Evidence for a 1-electron oxidation mechanism in N-dealkylation of N,N-dialkylanilines by cytochrome P450 2B1. Kinetic hydrogen isotope effects, linear free energy relationships, comparisons with horseradish peroxidase, and studies with oxygen surrogates. J Biol Chem 1996 271 27321-9. 

Figure 1 Comparison of the microbial direct versus indirect oxidation mechanism for sulfide (source Sand et al., 2001).

H202 or [PhIO] ocr c6H6 Mechanism of alkene oxidation elucidated comparison to corresponding metalloporphyrins made 323... 

A comparison of this proposed selective oxidation mechanism (Scheme 11) with three other important mechanisms from the literature (Table VI) (27) shows that there is a considerable amount of discrepancy between the assignment of the role of the individual metallic components of the catalyst (72). Matsuura (25), based on low-temperature adsorption studies, attributes chemisorption and first hydrogen abstraction to Mo, while in Haber s... 

A comparison between a HAS and a PAO as stabilizers against the oxidation of PP showed that they behave differently [4]. Based on experiment showing the ability of the HAS and the PAO to reduce the oxidation rate of decalin, squalane and decalin/lauryl aldehyde mixtures, it is shown that the HAS is mainly active in the presence of aldehydes. For unstabilized PP it is shown that aldehydes play an important role in its oxidation [5]. These results are used to propose an oxidation mechanism for PP and a mechanism underlying the action of HAS. 

Colloc h, N., Sopkova-de Oliveira Santos, J., et al. (2007). Protein crystallography under xenon and nitrous oxide pressure Comparison with in vivo pharmacology studies and implications for the mechanism of inhaled anesthetic action. Biophysical Journal, 92(1), 217-224. 

The data on the coefficients k12 = ki.i/ri and fe2 i = k2<2/r2 (Table 12) enables a comparison to be made between the reactivity of the H02-radical and that of peroxyacyl radicals with regard to the same substrate. It is quite surprising to note that ft1(1 is very different from k2%1 and ft1>2 from k2 2. In general, for hydrocarbons, ethers, and secondary alcohols [62], reactivity depends on the oxidized molecule and is independent of the active species. However, except that H02 is one radical compared with various hydrocarbon peroxidic radicals, it is possible that the cyclohexadiene oxidation mechanism is more complex than has been suggested and the interpretation of the results is uncertain. 

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