Indirect oxidation

Synthesis. The total aimual production of PO in the United States in 1993 was 1.77 biUion kg (57) and is expected to climb to 1.95 biUion kg with the addition of the Texaco plant (Table 1). There are two principal processes for producing PO, the chlorohydrin process favored by The Dow Chemical Company and indirect oxidation used by Arco and soon Texaco. Molybdenum catalysts are used commercially in indirect oxidation (58—61). Capacity data for PO production are shown in Table 1 (see Propylene oxide). 

Arco Chemical Bayport, Tex. Chaimelview, Tex. 1.05 indirect oxidation... 

There are many synthetic routes to alloxan. Probably the best is direct oxidation of barbituric acid (1004 R = H) with chromium trioxide (5208(32)6) but it may be made from barbituric acid via its benzylidene derivative by direct or indirect oxidation of uric acid from 5-chlorobarbituric acid (1004 R = C1) by nitration or from 5-nitrobarbituric acid (1004 R = N02) by chlorination, both via the intermediate (1005) (64M1057) or by permanganate oxidation of uracil (1006) under carefully controlled conditions (73BSF1167). 

The oxidation of hydrocarbons involves the sequential formation of a number of similar reactions in which various intermediate radicals which are combinations of carbon, hydrogen and oxygen are formed. In the simplest case, the oxidation of medrane, the methyl radical CH3 plays an important part both in direct oxidation to CO(g) and in indirect oxidation duough the formation of higher hydrocarbons such as CaHe before CO is formed. The chain reactions include... 

An alternative to the direct anodic oxidation of organic contaminants are the methods of indirect oxidation with the aid of oxidizers formed electrochemically in situ. These oxidizers (or mediators) can be obtained in both anodic and cathodic processes. Anodic agents are the salts of hypochloric acid (hypochlorites), the permanganates, the persulfates, and even ozone. 

The equivalent to allylic oxidation of alkenes, but with allylic transposition of the carbon-carbon double bond, can be carried out by an indirect oxidative process involving addition of an electrophilic arylselenenyl reagent, followed by oxidative elimination of selenium. In one procedure, addition of an arylselenenyl halide is followed by solvolysis and oxidative elimination. 

The Ce(III) thus obtained will next be oxidized at its decomposition potential (nearly 1.4 V) this overall process of direct and indirect oxidation continues until Fe(II) has been completely converted into Fe(III) at this stage no Ce(III) remains, but only the amount of Ce(IV) previously added in order to stop the anodic oxidation in time the potential of the Pt-WE (vs. SCE-RE) should automatically interrupt the electrolysis beyond say 1.5 V, i.e., well below the decomposition potential of H20. 

Indirect oxidation by attack of OH radicals formed in bulk solution or interface between the collapsing bubbles (Reactions 11.5 and 11.6)... 

Although there are indeed only few reported methods of direct activation of molecular oxygen via transition metals, there are many reports of indirect oxidation. The majority of this research is based on palladium-based oxidation as summarized in equation 32. The palladium complex catalyzed oxidation reactions have been reviewed previously186 and also only very recently187 and in this book the palladium catalyzed oxidation of dienes and polyenes will be discussed separately and therefore will not be discussed... 

The anodic reaction used is an indirect oxidation of benzene by Ag(I)/Ag(II) as redox mediator, because of its high faradaic yield. The high yield of BQ of 84% (of the theoretical yield) compared to the yield of the direct oxidation on the Pb02 anode of 62% indicates that some mechanism to minimize side reactions such as formation of o-BQ is operative. The highest yields are achieved with AgC104, (cf. Table 2, Ref. [66]). The use of AgC104 excludes its application in large scale synthesis. 

Epoxidation of olefins Propylene -> Propylene oxide U.S., Europe, Japan - Indirect oxidation via BrO, or cio-... 

Fig. 13. Continuous indirect oxidation of toluene and toluene derivatives using a cascade process. Pilotstate [140]...

Europe Europe, India 1,000 Ni anode in aqueous base Indirect oxidation via Br,... 

Methods for indirect oxidation have also been developed. The combination of KF/ wCPBA in acetonitrile and water has been used to generate KOF CH3CN reagent, a mild and selective oxidant that reacts at 0 °C with no overoxidation [78]. This reagent functions by providing a fluorosulfonium ion intermediate, which is hydrolyzed in the presence of water to the desired sulfoxides. As a result of the indirect oxidation method, the typical stereoselectivity of mCPBA-type oxidations is not observed here. The KOFCH3CN oxidant is similar in scope and mechanism to 1-fluoropyridinium triflates, Selectfluor [302] and the more classical t-butyl hypochlorite [288]. 

By indirect oxidation with electrogenerated NO3 radicals in f-butanol/ water/HN03/02, saturated hydrocarbons were oxidized to ketones with a statistical H-abstraction at the methylene... 

Some of these processes have been developed for technical conversions and have been summarized in Ref. [228, 229]. The anodic technical production of t-butylbenzaldehyde has been coupled with the cathodic reduction of phthahc anhydride to phthalide in a paired electrosynthesis in a capillary gap cell [230]. Indirect oxidations with Mn +/Mn + or as mediators... 

The reactions can be classified into two categories, direct and indirect oxidation methods, which are schematically represented in Figs. 1 and 2. 

The direct electrochemical oxidation of alcohols is in many cases unselective because of the high oxidation potentials of the alcohols. One possible way to avoid this disadvantage is the use of a mediatory system (an indirect oxidation). Thereby a mediator is converted to its oxidized form at a less positive potential than that required for the direct oxidation of the alcohol, and the oxidized form of the... 

Indirect oxidation of carbonyl compounds using mediators leads to better results than the direct oxidation. 

I n addition to the direct oxidation of simple amides, indirect oxidations of amides have proven useful for synthesizing chiral starting materials. Such reactions are often employed when direct electrolyses... 

In addition to using indirect oxidation reactions, electroauxiliaries have been used to circumvent problems with problematic amide oxidations. As mentioned in Sect. 10.2.2, an electroauxiliary is a group that is added to a molecule in order to reduce the oxidation potential of the... 

Indirect oxidations of amides by electrogenerated C1+ , which gives an adduct with the amide nitrogen, has been used to synthetize chiral building blocks (Scheme 37) [55]. 

Indirect Oxidation with Other Redox Systems. 508... 

Indirect Oxidation with Metal Ion Redox Systems. 509... 

Indirect Oxidation with Nickel (Ni) and Cobalt (Co) Compounds. .. 509... 

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