Oxidation reactions of sulfides

The use of dimethyldioxirane in the oxidation reactions of sulfides deserves to be mentioned [83, 84] as this mild neutral oxygen transfer reagent allows, for instance, highly reactive compounds such as a-oxosulfones to be obtained. Although the oxidation can usually be controlled at the sulfoxide level by using a stoichiometric amount of the... 

Most important in the classification of sulfur bacteria is the distinction between phototrophic and chemotrophic sulfur bacteria. Phototrophic (purple or green) bacteria use light as energy source to reduce CO2 to carbohydrates. Reduced sulfur compounds are used as an electron donor for this reduction, which takes place under anaerobic conditions. The oxidation reactions of sulfide to sulfur and sulfate by phototrophic bacteria are called the Van Niel reactions ... 

In oxidation reaction of sulfides with hydrogen peroxide, ZrCU was used as a promoter of the reaction. As shown in Equation 79, benzyl sulfide (180) was selectively converted into the corresponding sulfoxide (181) or sulfone (182), almost... 

In this paper we give a synopsis of the method as it is presently developed. It is exemplified by our two latest discoveries the oscillating oxidation reactions of sulfide and oxalic acid by persulfate. 

Rhenium oxides have been studied as catalyst materials in oxidation reactions of sulfur dioxide to sulfur trioxide, sulfite to sulfate, and nitrite to nitrate. There has been no commercial development in this area. These compounds have also been used as catalysts for reductions, but appear not to have exceptional properties. Rhenium sulfide catalysts have been used for hydrogenations of organic compounds, including benzene and styrene, and for dehydrogenation of alcohols to give aldehydes (qv) and ketones (qv). The significant property of these catalyst systems is that they are not poisoned by sulfur compounds. 

The oxidation of sulfides to sulfoxides are occasionally found to be unsatisfactory, since the resulting sulfoxides are easily oxidized to sulfones. In order to avoid the further oxidation of sulfoxides into sulfones, several oxidizing agents have been selected. Recently, we found that BTMA Bt3 is the most effective and satisfactory oxidizing agent for this purpose. That is, the reaction of sulfides with a calculated amount of BTMA Br3 and aq. sodium hydroxide in dichloromethane at room temperature, or in 1,2-dichloroethane under reflux, gave sulfoxides in good yields (Fig. 28) (ref. 36). 

The major metabolic pathway for hydrogen sulfide in the body is the oxidation of sulfide to sulfate, which is excreted in the urine (Beauchamp et al. 1984). The major oxidation product of sulfide is thiosulfate, which is then converted to sulfate the primary location for these reactions is in the liver (Bartholomew et al. 1980). 

The genus Thiobacillus, especially the species T. denitrificans catalyzed the oxidation reactions of hydrogen sulfide yielding soluble hydrosulfide compounds, elemental sulfur, and sulfuric acid. Carbonyl sulfide and carbon disulfide are converted to hydrogen sulfide by hydrolysis. Additionally, they are oxidized to SOx and sulfates via microbial action. The reported oxidation reactions of thiosulfate using nitrate as electron acceptor are ... 

Peroxynitrite easily oxidizes nonprotein and protein thiyl groups. In 1991, Radi et al. [102] have shown that peroxynitrite efficiently oxidizes cysteine to its disulfide form and bovine serum albumin (BSA) to some derivative of sulfenic acid supposedly via the decomposition to nitric dioxide and hydroxyl radicals. Pryor et al. [124] suggested that the oxidation of methionine and its analog 2-keto-4-thiomethylbutanic acid occurred by two competing mechanisms, namely, the second-order reaction of sulfide formation and the one-electron... 

Acid drainage results from the reaction of sulfide minerals with oxygen in the presence of water. As we show in this section, water in the absence of a supply of oxygen gas becomes saturated with respect to a sulfide mineral after only a small amount of the mineral has dissolved. The dissolution reaction in this case (when oxygen gas is not available) causes little change in the water s pH or composition. In a separate effect, it is likely that atmospheric oxygen further promotes acid drainage because of its role in the metabolism of bacteria that catalyze both the dissolution of sulfide minerals and the oxidation of dissolved iron (Nordstrom, 1982). 

In addition to a better understanding of the reaction of sulfide with ferric oxides and its role in pyrite formation, a more exact definition of the term reactive iron is critical. Does reactive iron mean a different iron oxide fraction for bacterial dissolution (e.g., weathering products such as goethite or hematite) than for reaction with sulfide (e.g., reoxidized lepidocrocite) In other words, is there a predigestion of ferric oxides by bacteria that allows a subsequent rapid interaction of sulfide with ferric oxides ... 

The oxidative imination of sulfides and sulfoxides via nitrene transfer processes leads to N-substituted sulfilimines and sulfoximines. This reaction is interesting as chiral sulfoximines are efficient chiral auxiliaries in asymmetric synthesis, a promising class of chiral ligands for asymmetric catalysis and key intermediates in the synthesis of pseudopeptides [169]. However, very few examples of such iron-catalyzed transformations have been described. 

Similarly to Mb, Hb is also active in the catalytic oxidation of substrates by hydrogen peroxide, with rates and general behavior comparable with those of Mb. In particular, a number of research reports showed that Hb exhibits oxidizing activities and can be used as a mimetic peroxidase to catalyze the oxidation reactions of aromatic compounds [180-182], aniline [183, 184], lipids [185], styrene [186], and sulfides [187]. Again, although the activity of Hb is not comparable with... 

Sand et al. (2001) suggested that Fe(III) ions or protons (H ) are the only chemical agents that dissolve a metal sulfide, and that bacteria have functions to regenerate these ions and to concentrate them at the mineral/water or the mineral/ bacterial cell interface. The chemical reactions require the presence of surrounding bacterial cells. The concentration of reactants in this nano-meter-thick layer causes the observed acceleration of rates of oxidative dissolution of sulfide minerals. 

Oxidations with m-chloroperoxybenzoic acid are carried out in solutions in hexane, dichloromethane, chloroform, methanol, or tetrahydro-furan at temperatures ranging from -78 to 40 C. The applications of m-chloroperoxybenzoic acid are epoxidation [287, 314, 315, 316] the Baeyer-Villiger reaction [286, 315, 317, 378] and the oxidation of primary amines to nitro compounds [379], of tertiary amines to amine oxides [320], of sulfides to sulfoxides [327, 322, 323, 324], and of selenides to selenones [325]. Secondary alcohols are oxidized to ketones in the presence of hydrogen chloride [326], and acetals are oxidized to esters with boron trifluoride etherate as a catalyst [327]. The addition of potassium fluoride to reaction mixtures facilitates product isolation, because both m-chloroben-zoic acid and the unreacted m-chloroperoxybenzoic acid are precipitated... 

The most important metabolic reaction is the assimilation of sulfur into organic forms which ultimately require the reduction of oxidized sulfur to the oxidation level of sulfide. This reduction is effected by the majority of microorganisms (bacteria, algae, fungi) and plants and, because of its abundance, sulfate is the dominant precursor of reduced sulfur. Pathways of assimilatory sulfate reduction are discussed briefly in Chapter 6.2 and depicted in Fig. 6.2.1 (p. 317). 

The regeneration of the spent sorbent is based on the oxidation reaction of the metal sulfide ... 

The asymmetric oxidation reaction of prochiral poly(ester 0-sulfide)s to optically active poly(ester 0-sulfoxide)s can be accomplished with almost theoretical chemoselactivity and moderate to high enantioselectivity degrees. While the asymmetric oxidation of prochiral sulfides should not be a preparative method for chiral sulfoxides, we expect that the structure of the parent polymers might be specifically designed for the preparation of chiral thermotropic poly(ester 0-sulfoxi-de)s. 

Thermogravimetric and Differential Thermal Analysis has been performed on Cat D. The TG and DTA profiles in Fig 2 show three different steps. The first one is the evaporation of hydrocarbons up to 200 °C with a moderate endotherm. The second step is the oxidation reaction of metal sulfides to oxides (most of the Mo sulfide, and part of the Co sulfide), starting around 200-250 °C. The third step around 350-450 °C is strongly exothermic, due to carbon burn-off as well as the remaining of sulfides oxidation. The carbon bum-off reaction finishes around 500 °C in this experiment performed on a dynamic mode at the heating-up rate of 5 °C/min. 

Benzisothiazolones 385 containing sulphur leaving groups were prepared via thioderivatives 383 [103,124]. The functionahsation of the nitrogen atom with a sulphur containing chain was achieved in two different ways depending on the substituent linked to the sulphur atom. The first one consists in the reaction of sulfides 384 (R = Me, Ph) with the sodium salt of saccharin 363 (R = H) in DMF affording 383. Alternatively, compounds 383 (25-60 overall yields) were prepared from the chloromethyl derivative 365 (R = H) and the appropriate mercaptan in the presence of DBU/MeCN or TEA/THF. Thiophenol reacted with bromo derivative 368 (R = H) in the presence of TEA. Sulfones n = 2) or sulfoxides (n = 1) 385 were prepared with m-chloroperbenzoic acid and their distribution depended on the stoichiometry of the oxidant and on the kind of R and R on 383 (Scheme 92). 

The use of transition-metal (Ti, Mo, V, Fe, W, Re, Ru) complexes as active catalysts for the selective oxidation of thioethers by H2O2 in homogeneous conditions has been reported by various authors [3-10]. Recently, it has been shown that some of these metals (Ti,V) incorporated in a zeolitic framework, such as MFI or MEL, are able to catalyse the oxidation reaction of thioethers with H2O2 [11,12]. However, no detailed studies on this reaction are available. The scope of this work was to investigate the influence of thioether structure, solvent nature, reaction temperature and shape selectivity effect of catalyst on the performances of TS-1 and Ti-beta samples in the sulfoxidation of organic sulfides with H2O2... 

TS-1 (pore diameter 0.55 nm) and Ti-beta (pore diameter 0.7 nm) have been tested in the oxidation reaction of two aliphatic sulfides, ethyl sulfide (Et2S) and butyl sulfide (BU2S), in methanol (MeOH) and tert-butanol (t-BuOH) as solvents. The results obtained show that thioether conversion highly depends on the nature of the catalyst (Fig. 1). 

Figure 4. Proposed complex intermediate for the oxidation reaction of organic sulfides by H2O2 over Ti-containing zeolites, in ROH type solvent.

These results can be explained by the relative rates of the formation of the sulfoxide (step a) and of the corresponding sulfone (step b) in the oxidation reaction of thioethers (reaction 1). It is known that, for dialkyl sulfides, such as Et2S, Pr2S and BU2S, sulfoxide formation proceeds much faster than sulfone formation [1], For the allyl sulfide the selectivity in sulfoxide is lower, because the difference in the rates of the two steps (a) and (b) of the oxidation reaction is less important, due to the conjugation of the lone electron pairs on the sulfur atom with the unsaturated system [1],... 

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