Oxidation primary

Fluxes are usually added in the form of either limestone or dolomite. The fluxes provide the basic constituents (CaO and MgO) needed to balance the acid constituents (Si02 and AI2O2) from the coke and ore. These are the four primary oxides which form the slag, although minor amounts of other oxides such as MnO, Na20, K2O, P2 S Ti02, and sulfur are also present. Proper adjustment of the slag chemistry is necessary to obtain the desired... 

Zinc dialkyl dithiophosphates are the primary oxidation inhibitors in combining these functions with antiwear properties in automotive oils and high pressure hydrauhc fluids. Their production volume is followed by aromatic amines, sulfurized olefins, and phenols (22). 

What is the for the light-generated primary oxidant of photosystem II if the light-induced oxidation of water (which leads to Og evolution) proceeds with a AG° of —25 kj/mol ... 

In contrast to the steric effoits, the purely electronic influences of substituents are less clear. They are test documented by linear free-energy relationships, which, for the cases in question, are for the most part only plots of voltammetrically obtained peak oxidation potentials of corresponding monomers against their respective Hammett substituent constant As a rule, the linear correlations are very good for all systems, and prove, in aax>rdance with the Hammett-Taft equation, the dominance of electronic effects in the primary oxidation step. But the effects of identical substituents on the respective system s tendency to polymerize differ from parent monomer to parent monomer. Whereas thiophenes which receive electron-withdrawing substituents in the, as such, favourable P-position do not polymerize at all indoles with the same substituents polymerize particularly well... 

The OH radical is a primary oxidizer in the atmosphere, oxidizing CO to CO2 and CH4 and higher hydrocarbons to CH2O, CO, and eventually CO2. OH and other radical intermediates can oxidize CH4 and NO in the following sequence of reactions ... 

In the rabbit, the nonplanar PCB 2,2, 5,5 -tetrachlorobiphenyl (2,2, 5,5 -TCB) is converted into the 3, 4 -epoxide by monooxygenase attack on the meta-para position, and rearrangement yields two monohydroxymetabolites with substitution in the meta and para positions (Sundstrom et al. 1976). The epoxide is also transformed into a dihydrodiol by epoxide hydrolase attack (see Chapter 2, Section 2.3.2.4). This latter conversion is inhibited by 3,3,3-trichloropropene-l,2-oxide (TCPO), thus providing strong confirmatory evidence for the formation of an unstable epoxide in the primary oxidative attack (Forgue et al. 1980). 

In the examples given, there is good evidence for the formation of an unstable epoxide intermediate in the production of monohydroxymetabolites. However, there is an ongoing debate about the possible operation of other mechanisms of primary oxidative attack that do not involve epoxide formation, for example, in the production of 2 OH 3,3, 4,4 -TCB (Figure 6.3). As mentioned earlier, P450s of gene family 1 (CYP 1) tend to be specific for planar substrates, including coplanar PCBs they do not appear to be involved in the metabolism of nonplanar PCBs. On the other hand. 

Inspired by Gif or GoAgg type chemistry [77], iron carboxylates were investigated for the oxidation of cyclohexane, recently. For example, Schmid and coworkers showed that a hexanuclear iron /t-nitrobenzoate [Fe603(0H) (p-N02C6H4C00)n(dmf)4] with an unprecedented [Fe6 03(p3-0)(p2-0H)] " core is the most active catalyst [86]. In the oxidation of cyclohexane with only 0.3 mol% of the hexanuclear iron complex, total yields up to 30% of the corresponding alcohol and ketone were achieved with 50% H2O2 (5.5-8 equiv.) as terminal oxidant. The ratio of the obtained products was between 1 1 and 1 1.5 and suggests a Haber-Weiss radical chain mechanism [87, 88] or a cyclohexyl hydroperoxide as primary oxidation product. 

Thus, Ip (inductor peroxide, primary oxide) derived from I d is converted by Ac d into the end-product, I(,x, which is inactive regarding the induction, i.e. coupling cannot turn into catalysis. Moreover, since there are several consecutive steps, and since the direct reaction between actor and acceptor is very slow, it follows that the value of Fj will not be changed by altering the ratio, ([Ac]/[I])o. However, in most cases studied the function Fj = /(Ac/I)q attains a limiting value, or at least varies therefore it has to be concluded that Manchot s concept cannot be maintained in its original form. 

If we try to interpret reaction (10) according to Manchot s concept, taking m and n as oxidation numbers of inductor before and after the reaction and y as oxidation number of the primary oxide , since (y— ) equivalents are consumed in the oxidation of acceptor we get... 

A number of methods are available for following the oxidative behaviour of food samples. The consumption of oxygen and the ESR detection of radicals, either directly or indirectly by spin trapping, can be used to follow the initial steps during oxidation (Andersen and Skibsted, 2002). The formation of primary oxidation products, such as hydroperoxides and conjugated dienes, and secondary oxidation products (carbohydrides, carbonyl compounds and acids) in the case of lipid oxidation, can be quantified by several standard chemical and physical analytical methods (Armstrong, 1998 Horwitz, 2000). 

Degradation of the insecticide chlorpyrifos has been examined in solutions of aqueous chlorine in which the primary oxidant is hypochlorous acid/hypochlorite. The final product was 2,3,5-trichloropyrid-2-one produced either directly, or via initial oxidative conversion of the thioate ester by replacement of the sulfur with oxygen (Duirk and Collette 2006). An analogous oxidation was found with diazinon (Zhang and Pehkonen 1999). 

Alcohol abuse is a major clinical problem in many countries and has been the subject of investigation for many years by those interested in determining the molecular basis of ethanol-induced liver dam e (see Lieber, 1990). These intensive and extended efforts have revealed much about the metabolism of ethanol in the liver and about the toxicity of its primary oxidative product, acetaldehyde. They have not, however, folly elucidated the molecular mechanisms that lead to the typical features of alcoholic liver injury steatosis, necrosis and eventually cirrhosis. 

FIGURE 6.4 Reactions and products of the primary oxidation intermediates of a-tocopherol (1), the tocopheroxyl radical 2, ortho-quinone methide 3, and chromanoxylium cation 4. 

Syn-Dihydroxylation. When the reaction was first discovered, the syn-dihydroxylation of alkenes was carried out by using a stoichiometric amount of osmium tetroxide in dry organic solvent.56 Hoffman made the observation that alkenes could react with chlorate salts as the primary oxidants together with a catalytic quantity of osmium tetroxide, yielding syn-vicinal diols (Eq. 3.11). This catalytic reaction is usually carried out in an aqueous and tetrahydrofuran solvent mixture, and silver or barium chlorate generally give better yields.57... 

Metal oxide-mediated oxidation of methane using air as a primary oxidant is an alternative way to produce N2-free syngas. The concept is based on the oxidation of methane by transition metal oxides in high-oxidation state yielding syngas and corresponding metal oxide in a low-oxidation state ... 

D. Other Primary Oxidants, Mechanisms of Benzoyl Peroxide... 

The mechanistic aspects of peroxidase-like activity of Fem-TAMLs discussed so far concerned mainly the activation by 1 of primary oxidizing agents, such as in Table VI, characterized by... 

The reaction of ions with peroxyl radicals appears also in the composition of the oxidation products, especially at the early stages of oxidation. For example, the only primary oxidation product of cyclohexane autoxidation is hydroperoxide the other products, in particular, alcohol and ketone, appear later as the decomposition products of hydroperoxide. In the presence of stearates of metals such as cobalt, iron, and manganese, all three products (ROOH, ROH, and ketone) appear immediately with the beginning of oxidation, and in the initial period (when ROOH decomposition is insignificant) they are formed in parallel with a constant rate [5,6]. The ratio of the rates of their formation is determined by the catalyst. The reason for this behavior is evidently related to the fast reaction of R02 with the... 

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