Mechanism for the oxidation

A proposed mechanism for the oxidation of propylene to acrolein is by a first step abstraction of an allylic hydrogen from an adsorbed propylene by an oxygen anion from the catalytic lattice to form an allylic intermediate ... 

Scheme 23 Possible mechanism for the oxidation of silicon surfaces by molecular oxygen.

Figure 2.14. Reaction mechanisms for the oxidation of CO on the (110) surface of platinum (left) and on the reconstructed surface (right). See text for explanation.

Figure 9.17. Mars-Van Krevelen mechanism for the oxidation of CO on a metal oxide surface. A characteristic feature is that lattice oxygen is used to oxidize the CO, leaving a defect that is replenished in a separate step by oxygen from the gas phase.

DMN oxidative demethylation has been shown to be a liver mi-crosome cytochrome P-450 monooxygenase (10) Lotlikar et al. (11) found that a reconstituted enzyme system, consisting of cytochrome P-450, NADPH-cytochrome P-450 reductase and phosphatidyl choline was effective in catalyzing the demethylation of DMN. The most commonly accepted mechanism for the oxidative demethylation of DMN and, by extension, of other dialkyInltrosamlnes is shown in Scheme 1. 

Nelson L, I Shanahan, HW Sidebottom, J Treacy, OJ Nielsen (1990) Kinetics and mechanism for the oxidation of 1,1,1-trichloroethane. Int J Chem Kinet 22 577-590. 

Cabelli, D.E. and Bielski, B. (1983). Kinetics and mechanism for the oxidation of ascorbic acid (ascorbate by HO2/O2 radicals. A pulse radiolysis and stopped-flow photolysis study. J. Phys. Chem. 87, 1809. 

Within the general mechanism for the oxidation of Ci molecules, proposed by Bagotzsky, formic acid is one of the simplest cases, since it requires only the transfer of two electrons for the complete oxidation to CO2 [Bagotzky et al., 1977]. In fact, it has the same oxidation valency as CO both require two electrons for complete oxidation to CO2. When compared with CO, the reaction mechanism of formic acid is more complex although the catalysis of the oxidation reaction is much easier. In fact, formic acid can be readily oxidized at potentials as low as 0.2 V (vs. RHE). Its reaction mechanism takes place according to the well-established dual path mechanism [Capon and Parsons, 1973a, b] ... 

This oxidative process has been successful with ketones,244 esters,245 and lactones.246 Hydrogen peroxide can also be used as the oxidant, in which case the alcohol is formed directly.247 The mechanisms for the oxidation of enolates by oxygen is a radical chain autoxidation in which the propagation step involves electron transfer from the carbanion to a hydroperoxy radical.248... 

Takahama, U. Oniki T. Shimokawa H. A possible mechanism for the oxidation of sinapyl alcohol hy peroxidase-dependent reactions in the apoplast enhancement of the oxidation hy hydroxycinnamic acids and components of the apoplast. Plant Cell Physiol. 1996, 37, 499-504. 

This equation agrees with the chain mechanism for the oxidation of the 2-propanol, under the condition that H202 is the only source of radicals and the rate of initiation is v = /c,[H202],... 

IV. Mechanisms for the Oxidation Step From Pt(II)-Hydrocarbyl to Pt(TV)-Hydrocarbyl... 

A mechanism for the oxidation of S02 in the presence of V205 cafcalyts assumes that the catalyst alternately surrenders its oxygen to the S02 and is reoxidized by oxygen from the gas. These reactions are assumed to occur according to Regner Simecek (Coll Czech Chem Comm 33 2540, 1968). 

The transfer of redox equivalents can be achieved by an electrocatalyst (mediator) or a modified electrode. Indirect electrolysis can lead to a better selectivity due to the specific interaction of the mediator with the substrate. However, low turnovers and the need to separate the mediator from the product are possible disadvantages, as mentioned above. The nickel hydroxide electrode [195,196] is fairly free from these disadvantages. The following mechanism for the oxidation at the nickel hydroxide electrode has been proposed in the literature [195]. 

The following mechanism for the oxidation of Cr(III) to Cr(VI) on a Pb02 surface has been postulated. Pb02 operates as oxygen carrier anode... 

FIGURE 4.49 Mechanism for the oxidative rearrangement of (R)-pulegone to (7 )-menthofuran. 

FIGURE 4.74 Mechanism for the oxidation of terminal aryl alkynes. 

One possible mechanism for the oxidation of Mn(II) on an oxide surface is shown in Figure 2. The binding of Mn(II) to the surface may facilitate the electron transfer from Mn(II) to 02 (32). The surface groups on the metal oxide, if appropriately cooordinated, will exert a repulsive effect on the electron in the manganese dz orbital, making it easier for the 02 bound to the manganese atom to remove this electron. The nature of the products was not characterized so the overall reaction stiochiometry is unknown. 

Figure 2. A possible mechanism for the oxidation of Mn(II) a metal oxide surface.

Indeed, in developing complete mechanisms for the oxidation of CO and hydrocarbons applicable to practical systems over a wide range of temperatures and high pressures, it is important to examine the effect of the H02 reactions when the ratio is as high as 10 or as low as 0.1. Considering that for air combustion the total concentration (M) can be that of nitrogen, the boundaries of this ratio are depicted in Fig. 3.3, as derived from the data in Appendix C. These modem rate data indicate that the second explosion limit, as determined... 

Taking all these considerations into account, it is possible to postulate a general mechanism for the oxidation of aliphatic hydrocarbons namely,... 

Fig. 21 General mechanism for the oxidation of thiols to disulfides with selenoxides or telluroxides.

Trozzolo, A. M., and F. H. Winslow. A mechanism for the oxidative photod rada-tion of polyethylene. Macromolecules 1 98-100, 1968. 

Whatever the initial step of formation of surface silyl radicals, the mechanism for the oxidation of silicon surfaces by O2 is expected to be similar to the proposed Scheme 8.10. This proposal is also in agreement with the various spectroscopic measurements that provided evidence for a peroxyl radical species on the surface of silicon [53] during thermal oxidation (see also references cited in [50]). The reaction being a surface radical chain oxidation, it is obvious that temperature, efficiency of radical initiation, surface precursor and oxygen concentration will play important roles in the acceleration of the surface oxidation and outcome of oxidation. 

The direct electrochemical oxidation of alcohols involves removal of one electron from a non-bonding pair on oxygen. Relatively anodic potentials are required and the use of reagents, which can provide another mechanism for the oxidation step, has been extensively explored. Electrochemistry is then involved in the reoxidation of spent reagent and often the system can be adapted so as to require only a catalytic amount of reagent. 

Scheme 10 Catalytic mechanism for the oxidation of benzylamine to benzylidinebenzylamine using 23...

Scheme 17 Postulated mechanism for the oxidative polymerization of dimethylphe-nol [238]...

The data apparently require a free radical chain mechanism for the oxidation of benzhydrol. Potassium superoxide filtered from a completed oxidation completely removed the induction period for a fresh oxidation. Thus, potassium superoxide must either serve as an initiation of oxidation... 

Because of the lack of information in the literature on the radical reactions of compounds of quinquevalent phosphorus, it is impossible to postulate a readily acceptable mechanism for the oxidation of zinc dialkyl dithiophosphates. Colclough and Cunneen (7) rejected immediately the possibility of hydrogen abstraction, but in view of the present results serious consideration has been given to this reaction. During this work it was shown (15) that abstraction of hydrogen from trialkyl phosphates, trialkyl phosphonates, and sodium dialkyl phosphates can occur at room temperature in an aqueous medium in the presence of hydroxy radicals. 

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