Oxidation and Dehydrogenation

The epoxidation of enones by alkaline hydrogen peroxide is well known. Prolonged reaction causes C-C bond fission, probably by a Baeyer-Villiger mechanism. Applied to the 1 o,2a-epoxy-4,6-dien-3-one system (231), this 

Oxidation of the 3,4-seco-4-methyl-4-methylene compound (244) with selenium dioxide gave the unsaturated aldehyde (245). It is not known whether the aldehyde is derived from the 4-methyl group, or from the 4-methylene carbon 

Singlet excited oxygen ( Ag) has been considered to convert alkenes into allylic hydroperoxides (246) by a concerted mechanism (247). It now seems likely that reaction occurs via a per-epoxide (248), which subsequently rearranges as 

Androst-15-en-l 7-ones, of either configuration at C-14 (249), or androst-14-en-17-ones (250), are rapidly converted in air into the 14)8-hydroperoxy-derivative 

Cuilleron, M. F6tizon, and M. Golfier, Bull. Soc. chim. France, 1970, 1193. 

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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). 

PCSs obtained by dehydrochlorination of poly(2-dilorovinyl methyl ketones) catalyze the processes of oxidation and dehydrogenation of alcohols, and the toluene oxidation207. The products of the thermal transformation of PAN are also catalysts for the decomposition of nitrous oxide, for the dehydrogenation of alcohols and cyclohexene274, and for the cis-tnms isomerization of olefins275. Catalytic activity in the decomposition reactions of hydrazine, formic acid, and hydrogen peroxide is also manifested by the products of FVC dehydrochlorination... 

Itoh, N. and R. Govind, Combined oxidation and dehydrogenation in a palladium membrane, Ind. 

Selenium dioxide causes both oxidation and dehydrogenation of fused cycloheptenones to give indolotropolone [57LA(608)38], In the cases of furan 4a (54CB1197)and thiophene 4b [55LA(595)203], it effects twofold oxidation, yielding hydroxytropolones 11a and 11b, respectively (Scheme 4) ... 

Monocyclic tetrahydrophosphorin derivatives can be prepared, for example by dehydration of tertiary alcohols which are available by the action of lithium alkyls on 4-oxophos-phorinane derivatives (equation (16)). P- Oxidation and dehydrogenation of the ketone with Se02 is also possible (equation (17)) (66AG(E)588). Electrophilic substitution in position 2 (6) of phosphorinane 1-oxides and 1-sulfides can be achieved by a Wittig-Horner a-deprotonation, e.g. equation (18) (72BSF(2)402l, 79CJC723). 

Spinel oxides with a general formula AB2O4 (i.e. the so-called normal spinels) are important materials in industrial catalysis. They are thermally stable and maintain enhanced and sustained activities for a variety of industrially important reactions including decomposition of nitrous oxide [1], oxidation and dehydrogenation of hydrocarbons [2], low temperature methanol synthesis [3], oxidation of carbon monoxide and hydrocarbon [4], and oxidative dehydrogenation of butanes [5]. A major problem in the applications of this class of compound as catalyst, however, lies in their usually low specific surface area [6]. 

The metal ion is a typical catalyst for a reaction of Class B, but because H+ and OH- ions are formed in the process, the reaction may be expected to be pH dependent as well. The catalyst does not necessarily have to be a metal ion. Every substrate that can change oxidation state at the right potential and is capable of reacting with the hydrogen peroxide molecule in its two valency states can be considered a catalyst for this reaction. This means that the best parameter to correlate this reaction with would be the redox potential of the catalyst, which unfortunately is very difficult to measure on a solid material. The best thing to do is to use a catalyst which can be dissolved in a liquid medium of some kind, and to study the redox properties in the dissolved state. Measurements of this kind will be discussed in the section on oxidation and dehydrogenation. 

In oxidation and dehydrogenation correlations were found with the redox properties of the solid. In the decomposition of nitrous oxide the paramagnetic properties, and with them, the catalytic activity, of organic polymers could be changed at will by modifications in the polymer structure, and in acid catalysis activity could be regulated by changing the type of acidic group and by selective neutralization. 

Oxidation and Dehydrogenation.—Some novel oxidations of A -olefinic steroids are reported. Silver oxide, in refluxing benzene or toluene, converted cholesterol into the 6,6 -dimeric compound (148), probably through a one-electron process. The dimer decomposed above its m.p. to give an equimolar... 

Electrophilic Addition Other Addition Reactions Reduction of Unsaturated Steroids Oxidation and Dehydrogenation Miscellaneous Reactions... 

Although AI values may be useful to estimate the progress of the oligomerization of the nitrile groups and the subsequent oxidation and dehydrogenation processes, they cannot be recommended as a criterion for optimum stabilization, unless a careful investigation has been made as to which lA value is actually optimum for a particular precursor. AI values close to unity may easily be obtained by prolonged heat treat-... 

Following therapeutic doses, methyprylon is rapidly absorbed, with peak plasma levels occurring within 1 or 2h. Greater than 95% of a dose undergoes oxidation and dehydrogenation in the liver the remainder is excreted unchanged in the urine. At least... 

Selenium dioxide, Seienious acid, SeOj, HsSeOa. Mol. wts. 110.96,128.98. Suppliers Fairmont Chemical Co. K and K Laboratories Matheson, Coleman and Bell (SeOJ Fisher (HjSeO.,). Review and procedures for conversion of recovered Se into SeOa, In oxidations and dehydrogenations with either preformed seienious acid or selenium dioxide and water, usually in acetic acid, ethanol, or dioxane, the solution turns yellow and then red, and later some of the selenium separates in a red form difficult to Alter, some is retained in colloidal solution, and some is bound to an oraanic lubitrita. Elimination of all loleniuin fVom a reaction mixture often oreienti... 

In this section we deal with hydrocarbons and their adsorption and reaction on metals. The first papers illustrate typical research into bonding of species to surfaces and the units or fragments formed by hydrocarbons upon adsorption. After a brief mention of oxidation and dehydrogenation the remainder of the section is devoted to the appearance of carbonaceous species on the surfaces of catalysts and their role, if any, in catalysis. 

Chhikara and coworkers [17] have reported that ionic liquids are excellent reaction media for the oxidation and dehydrogenation of steroids with IBX. In a systematic study, they investigated the efficacy of the oxidation of cyclic secondary alcohols with IBX in [bmun][Br] (Scheme 14.17). They noticed that the nature of the products formed is influenced by several factors such as the relative ratio of IBX, quantity of IBX, and temperature of the reaction. For example, when 1.2 eq. of IBX was... 

The necessary reaction paths have now been established. The catalyst must promote oxygen insertion and mild dehydrogenation but inhibit strong oxidation and dehydrogenation. 

Jurva et al. performed comprehensive studies on the comparability of EC-MS and cytochrome P 450 catalyzed reactions [48,49] and found that EC-MS successfully mimicked those CYP reactions that are initiated by a one-electron oxidation, such as /V-dealkylation, 5-oxidation, / -oxidation, alcohol oxidation, and dehydrogenation, whereas the reactions that are initiated via direct hydrogen atom abstraction, for example, O-dealkylation and hydroxylation of unsubstituted aromatic rings, were not mimicked. In the latter cases the oxidation potentials were too high for electrochemical oxidation in aqueous solutions. A further disadvantage is that EC lacks the stereospecifity of the reactions, in contrast to CYP catalyzed reactions [50],... 

Braunschweigische Maschinenbauanstalt has developed a thermally balanced process in the reaction section by combining oxidation and dehydrogenation. In this process, an air/ethanol/steam mixture is treated in the presence of a silver base catalyst, and the yield of the operation approaches 93 molar per cent. 

It has been thought that the acid-base character is an intrinsic property of oxide substrates. The selectivity in the catalytic decomposition reaction of formic acid has been used to scale the acid-base property dehydration over acidic oxide and dehydrogenation over basic oxide, though this classification is over simplified vide infra. 

Becker, H.-D. Quinones as oxidants and dehydrogenating agents. In The chemistry of the quinonoid compounds. Patai, S. (ed.). London-New York-Sydney-Toronto Wiley 1974, pp. 335-424... 

Scheme 9. Oxidation and dehydrogenation products of bulbocapnine methyl ether (25f)...

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