Dehydrogenative oxidation

Pd(0) catalyzed Dehydrogenation (oxidation) of AAlyl Carbonates (Tsuji Oxidation) Tetrahedron 1986, 42, 4361... 

Oxidation can also occur at the central metal atom of the phthalocyanine system (2). Mn phthalocyanine, for example, can be produced ia these different oxidation states, depending on the solvent (2,31,32). The carbon atom of the ring system and the central metal atom can be reduced (33), some reversibly, eg, ia vattiag (34—41). Phthalocyanine compounds exhibit favorable catalytic properties which makes them interesting for appHcations ia dehydrogenation, oxidation, electrocatalysis, gas-phase reactions, and fuel cells (qv) (1,2,42—49). 

The chemistry of ethyl alcohol is largely that of the hydroxyl group, namely, reactions of dehydration, dehydrogenation, oxidation, and esterification. The hydrogen atom of the hydroxyl group can be replaced by an active metal, such as sodium, potassium, and calcium, to form a metal ethoxide (ethylate) with the evolution of hydrogen gas (see Alkoxides, metal). 

There are two ways to produce acetaldehyde from ethanol oxidation and dehydrogenation. Oxidation of ethanol to acetaldehyde is carried out ia the vapor phase over a silver or copper catalyst (305). Conversion is slightly over 80% per pass at reaction temperatures of 450—500°C with air as an oxidant. Chloroplatinic acid selectively cataly2es the Uquid-phase oxidation of ethanol to acetaldehyde giving yields exceeding 95%. The reaction takes place ia the absence of free oxygen at 80°C and at atmospheric pressure (306). The kinetics of the vapor and Uquid-phase oxidation of ethanol have been described ia the Uterature (307,308). 

Acetone (2-propanone), is produced from isopropanol by a dehydrogenation, oxidation, or a combined oxidation dehydrogenation route. 

Subsequent cyclizations, dehydrogenations, oxidations, etc., lead to the individual naturally occurring carotenoids, but little is known about the biochemistry of the many interesting final structural modifications that give rise to the hundreds of diverse natural carotenoids. The carotenoids are isoprenoid compounds and are biosynthesised by a branch of the great isoprenoid pathway from the basic C5-terpenoid precursor, isopentenyl diphosphate (IPP). The entire biosynthesis takes place in the chloroplasts (in green tissues) or chromoplasts (in yellow to red tissues). 

The enzyme isocitrate dehydrogenase is one of the enzymes of the Krebs or citric acid cycle, a major feature in carbohydrate metabolism (see Section 15.3). This enzyme has two functions, the major one being the dehydrogenation (oxidation) of the secondary alcohol group in isocitric acid to a ketone, forming oxalosuccinic acid. This requires the cofactor NAD+ (see Section 11.2). For convenience, we are showing non-ionized acids here, e.g. isocitric acid, rather than anions, e.g. isocitrate. 

Platinum also is used extensively as a catalyst in hydrogenation, dehydrogenation, oxidation, isomerization, carbonylation, and hydrocracking. Also, it is used in organic synthesis and petroleum refining. Like palladium, platinum also exhibits remarkable abdity to absorb hydrogen. An important application of platinum is in the catalytic oxidation of ammonia in Ostwald s process in the manufacture of nitric acid. Platinum is installed in the catalytic converters in automobile engines for pollution control. 

In the middle thirties the reactions of naphtha and certain compounds known to be present in naphtha were being studied in university and industrial laboratories. One of the problems was to find a catalyst that was capable of synthesizing an aromatic from a paraffin. It was reasoned that the hydrogenation-dehydrogenation oxide-type catalysts such as molybdenum oxide and chromium might possess suitable activity at temperatures well below those employed in thermal reforming. 

Dehydrogenation Oxidation of the products formed in the above reaction yields a-p-unsaturated acyl CoA derivatives. This reac tion is analagous to the dehydrogenation described in the p-oxidation scheme of fatty acid degradation (see p. 190). 

Oxidation reactions (see also Addition reactions to carbon-carbon multiple bonds, Allylic reactions, Aromatiza-tion, Dehydrogenation, Oxidative cleavage, Oxidative coupling, Ozo-nolysis)... 

Phthalocyanine compounds exhibit favorable catalytic properties which makes them interesting for applications in dehydrogenation, oxidation, eleclrocalalysis, gas-phase rcacliuns, and fuel cells. 

Within the following subsections the stability of the bicyclic ring system, plus the hydrogenation, reduction, dehydrogenation, oxidation, and quater-nization of the compounds are reviewed. This is followed by discussion of substitution reactions affecting the pyrido [ 1,2-a]pyrimidine ring, transformations of the side chains, and finally ring transformation reactions. 

Experimental studies of conjugated reactions—dehydrogenation, oxidation, hydrogenol-ysis and nitrogen fixation. 

The reactions in Scheme 1 are achieved by three processes - dehydrogenation, oxidative dehydrogenation, and dehydrocyclization. 

An attempt to produce indenols via RCM reaction of the parent dienes, in the presence ofRuCl2(= CHPh)(imidazolinylidene)(PCy3) at 80 °C, actually led to the corresponding indenones [87]. Whereas the indenols are obtained at room temperature, it was shown that the alkene metathesis ruthenium catalyst is also responsible for the dehydrogenative oxidation of indenols at 80 °C (Scheme 41). 

Catalytic transformations of terpenes are well documented [213-215], comprising a wide variety of reactions hydrogenation, dehydrogenation, oxidation, hy-droformylation, carbonylation, hydration, isomerization and rearrangement, and cyclization. 

Acetaldehyde Oxidation. Ethanol [64-17-5] is easily dehydrogenated oxidatively to acetaldehyde (qv) using silver, brass, or bronze catalysts. Acetaldehyde can then be oxidized in the liquid phase in the presence of cobalt or manganese salts to yield acetic acid. Peracetic acid [79-21-0] formation is prevented by the transition metal catalysts (7). (Most transition metal salts decompose any peroxides that form, but manganese is uniquely effective.)... 

Lattice silver also can perform a dehydrogenative oxidation of alcohols with O2. For example, fert-butyl alcohol can be oxidized to isobutylene oxide on an O2 covered Ag(l 10) surface at elevated temperatures (85). However, other oxidation products also were produced. Experiments using 02 labeling revealed that the oxygen in the product is from the original alcohol and they believe the hydrogen atom from the methyl C—H bond is directly transferred to either O2 or another molecule of tcrf-butyl alcohol. Lattice silver is still widely used in industry and further studies hold promise for other industrially suitable methods (Fig. 14). 

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