Oxidation of organic substrates

Inferences that oxidation takes place on the photocatalyst s surface have been made (67). No such conclusions can be drawn. Similar observations have been made in homogeneous media if a bimolecular reaction between two reactants is assumed. A Langmuir-type behavior is no guarantee of a surface occurring process. A rigorous treatment (68) of the kinetics involved in the photocataly2ed oxidations of organic substrates on an irradiated semiconductor has confirmed this. 

During the accelerating process, regeneration of redox mediator can be linked to the anaerobic oxidation of organic substrates by microorganisms. 

Oxidation of organic substrates with molecular oxygen on nickel complexes is limited to a few known examples. 

Tejel C, Ciriano MA (2007) Catalysis and Organometallic Chemistry of Rhodium and Iridium in the Oxidation of Organic Substrates. 22 97-124 Tekavec TN, Louie J (2006) Transition Metal-Catalyzed Reactions Using N-Heterocyclic Carbene Ligands (Besides Pd- and Ru-Catalyzed Reactions). 21 159-192 Tesevic V, see Gladysz JA (2008) 23 67-89... 

Hydroperoxides play an important role as oxidants in organic synthesis [56-58]. Although several methods are available for the preparation of racemic hydroperoxides, no convenient method of a broad scope was until recently [59] known for the synthesis of optically active hydroperoxides. Such peroxides have potential as oxidants in the asymmetric oxidation of organic substrates, currently a subject of intensive investigations in synthetic organic chemistry [60, 61]. The application of lipoxygenase [62-65] and lipases [66,67] facilitated the preparation of optically active hydroperoxides by enzymes for the first time. 

Cerium(IV) oxidations of organic substrates are often catalysed by transition metal ions. The oxidation of formaldehyde to formic acid by cerium(IV) has been shown to be catalysed by iridium(III). The observed kinetics can be explained in terms of an outer-sphere association of the oxidant, substrate, and catalyst in a pre-equilibrium, followed by electron transfer, to generate Ce "(S)Ir", where S is the hydrated form of formaldehyde H2C(OH)2- This is followed by electron transfer from S to Ir(IV) and loss of H+ to generate the H2C(0H)0 radical, which is then oxidized by Ce(IV) in a fast step to the products. Ir(III) catalyses the A -bromobenzamide oxidation of mandelic acid and A -bromosuccinimide oxidation of cycloheptanol in acidic solutions. ... 

Effect of pH on Lignin Peroxidase Catalysis. The oxidation of organic substrates by lignin peroxidase (Vmax) has a pH optimum equal to or possibly below 2. Detailed studies have been performed on the pH dependency of many of the individual reactions involved in catalysis. The effect of pH on the reaction rates between the isolated ferric enzyme, compounds I or II and their respective substrates has been studied. Rapid kinetic data indicate that compound I formation from ferric enzyme and H2O2 is not pH dependent from pH 2.5-7.5 (75,16). Similar results are obtained with Mn-dependent peroxidase (14). This is in contrast to other peroxidases where the pKa values for the reaction of ferric enzyme with H2O2 are usudly in the range of 3 to 6 (72). 

Over the past decade, NHPI has emerged as a powerful and popular catalyst for organic oxidation reactions where, together with acetaldehyde, it has been employed as oxidation mediator . The use of molecular oxygen for the selective oxidation of organic substrates, especially hydrocarbons under mild conditions, is still a major challenge for organic chemistry. It constitutes an environmentally safe alternative to more... 

Partial oxidation of organic substrates that is carried out catalytically in a chemo-, regio-, and stereoselective manner is an area of intense worldwide activity 4,5,9,165-167). Synthetic transition metal catalysts and enzymes have contributed successfully, but major challenges remain. Many of problematic transformations are not easily (or not all) accomplished by synthetic transition metal catalysts. Such cases form ideal targets for directed evolution. 

R. P. Farrell and P. A. Lay, New Insights into the structure and reactions of chromium (V) complexes. Implications for chromium(VI) and chromium(V) oxidations of organic substrates and the mechanism of chromium-induced cancers, Comments Inorg. Chem., 13 (1992) 133-175. 

Abstract This chapter principally concerns oxidations of organic substrates containing N, O, S, P, As and Sb. Oxidations of amines are covered first, including primary amines to nitriles or amides secondary amines to imines or other products tertiary amines to N-oxides or other prodncts (Section 5.1) and the oxidation of amides (5.2). Oxidation of ethers to esters or lactones follows (5.3), then of sulfides to sulfoxides or sulfones (5.4) and of phosphines, arsine and stibines to their oxides (5.5). A final section (5.6) concerns such miscellaneous oxidations not covered by other sections in the book. 

Ruthenium was the last of the platinum-group elements to be discovered, and has perhaps the most interesting and challenging chemistry of the six. In this book just one major aspect is covered its ability, mainly by virtue of its remarkably wide range of oxidation states which exist in its many complexes (from +8 to -2 inclusive) to effect useful and efficient oxidations of organic substrates. 

So-called blue multinuclear copper oxidase enzymes, such as laccase and ascorbate oxidase, catalyze the stepwise oxidation of organic substrates (most likely in successive one-electron steps) in tandem with the four-electron reduction of O2 to water, i.e. no oxygen atom(s) from O2 are incorporated into the substrate (Eq. 4) [15]. Catechol oxidase, containing a type 3 center, mediates a two-electron substrate oxidation (o-diphenols to o-chinones), and turnover of two substrate molecules is coupled to the reduction of O2 to water [34,35]. The non-blue copper oxidases, e.g. galactose oxidase and amine oxidases [27,56-59], perform similar oxidation catalysis at a mononuclear type 2 Cu site, but H2O2 is produced from O2 instead of H2O, in a two-electron reduction. 

Catalysis and Organometallk Chemistry of Rhodium and Iridium in the Oxidation of Organic Substrates... 

Abstract The purpose of this chapter is to present a survey of the organometallic chemistry and catalysis of rhodium and iridium related to the oxidation of organic substrates that has been developed over the last 5 years, placing special emphasis on reactions or processes involving environmentally friendly oxidants. Iridium-based catalysts appear to be promising candidates for the oxidation of alcohols to aldehydes/ketones as products or as intermediates for heterocyclic compounds or domino reactions. Rhodium complexes seem to be more appropriate for the oxygenation of alkenes. In addition to catalytic allylic and benzylic oxidation of alkenes, recent advances in vinylic oxygenations have been focused on stoichiometric reactions. This review offers an overview of these reactions... 

In air-saturated or oxygen-saturated solution, molecular Oa participates as an oxidizing agent in the photosensitized oxidation of organic substrates. When an addition product A02, a peroxide, is formed ... 

The formation and decomposition of Crv in aqueous and non-aqueous media during the oxidation of organic substrates such as oxalic acid and ethylene glycol by potassium dichromate has been recognized for some time. No study resulted in the isolation of a stable, well-characterized chromium(V) complex until 1978 when potassium bis(2-hydroxy-2-methylbutyrato)oxochromate(V) monohydrate was prepared from chromium trioxide and the tertiary a-hydroxy acid in dilute perchloric acid according to equation (91). The Crv, which is... 

Metal/Metal-Oxide Couples Capable of Acting as Heterogeneous Mediators for the Oxidation of Organic Substrates Dissolved in Aqueous Solution... 

Oxidation of organic substrates with molecular oxygen as the oxygen source and catalyzed by metal surfaces is industrially very important reactions. E.g. is ethylene oxide is produced in about 1 x 10 ° kg/year on a silver surface with ethylene and molecular oxygen as reactants, phthalic anhydride and maleic anhydride are produced in about 2 x 109 and 4 x 108 kg/year on a vanadyl pyrophosphate surface with o-xylene and n-butane, respectively, as substrates and molecular oxygen as the oxygen donor (ref. 1). 

M.A.Fox "Photocatalytic Oxidation of Organic Substrates", in "Photocatalysis and Environment Trends and Applications", M.Schiavello (Ed.), NATO-ASI, Se ries C, Vol. 237, by Kluwer Academic Publishers, Dordrecht, The Netherlands, 1988, pp. 445-467. 

Only a small fraction of the total free energy content of glucose is released under anaerobic conditions. This is because no net oxidation of organic substrates can occur in the absence of oxygen. Catabolism under anaerobic conditions means that every oxidative event in which electrons are removed from an organic compound must be accompanied... 

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