Oxygen or Air

A wide range of aromatic and aliphatic alkenes were demonstrated in this system [26]. It was shown that both yield and enantioselectivity are influenced by the pH of the reaction medium. The procedure was also applied to practical syntheses of natural product derivatives [27]. This version of the AD reaction not only uses a more ecological co-oxidant, but also requires much less material 87 mg of material (catalyst, ligand, base, reoxidant) is required to oxidize 1 mmol of the same alkene instead of 1400 mg when AD mix is used. 

In 1999 the first AD reaction using molecular oxygen without any secondary electron transfer mediator was published [28]. Osmium(VI) was readily reoxidized to osmium(VIII) in this system. We demonstrated that the osmium-catalyzed dihydroxylation of aliphatic and aromatic alkenes proceeds efficiently in the presence of dioxygen under ambient conditions. This dihydroxylation procedure constitutes a significant advancement compared to other re-oxidation procedures (Table 1.2, entry 7). 

For a better comparison, a model reaction of the dihydroxylation of a-methylstyrene was examined using different stoichiometric oxidants. The yield of the 1,2-diol remained good to very good (73-99%), independently of the oxidant used. 

The best enantioselectivities (94-99% ee) were obtained with hydroquinidine 1,4-phthalazinediyl diether ((DHQD)2PHAL) as the ligand at 0-12 °C (Table 1.2, entries 1, 3, and 4). 

The dihydroxylation process with oxygen is clearly the most ecologically favorable procedure (Table 1.2, entry 7) if the production of waste from a stoichiometric 

25 mol% K2[0s02(0H)4l 2.3 mol% (DHQD)2PHAL 30 tnol% K2CO3 tert-BuOH/H2O,20°C 

The dihydroxylation process with oxygen is clearly the most ecologically favorable procedure (Table 1.2, entry 5), when the production of waste from a stoichiometric reoxidant is considered. With the use of K3[Fe(CN)6] as oxidant approximately 8.1 kg of iron salts per kg of product are formed. However, in the case of the Krief (Table 1.2, entry 3) and BackvaU procedures (Ikble 1.2, entry 4) as well as in the presence of NaOCl (Table 1.2, entry 6) some byproducts also arise due to the use of cocatalysts and co-oxidants. It should be noted that only salts and byproducts formed 

Entry Oxidant yield (%) Reaction conditions ee w TON Waste (oxidant) Ref. (kg/kg dhl)  

The dihydroxylation of a-methylstyrene in the presence of 1 bar of pure oxygen proceeds smoothly (Table 1.3, entries 1-2), with the best results being obtained at pH 10.4. In the presence of 0.5 mol% K2[0s02(0H)4]/1.5 mol% DABCO or 1.5 mol% (DHQD)2PHAL at pH 10.4 and 50 °C total conversion was achieved after 16 h or 20 h depending on the ligand. While the total yield and selectivity of the reaction are excellent (97% and 96%, respectively), the total turnover frequency of the catalyst is comparatively low (TOP = 10-12 h ). In the presence of the chiral cinchona ligand 

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Manufactured by the liquid-phase oxidation of ethanal at 60 C by oxygen or air under pressure in the presence of manganese(ii) ethanoate, the latter preventing the formation of perelhanoic acid. Another important route is the liquid-phase oxidation of butane by air at 50 atm. and 150-250 C in the presence of a metal ethanoate. Some ethanoic acid is produced by the catalytic oxidation of ethanol. Fermentation processes are used only for the production of vinegar. 

Fuels which have been used include hydrogen, hydrazine, methanol and ammonia, while oxidants are usually oxygen or air. Electrolytes comprise alkali solutions, molten carbonates, solid oxides, ion-exchange resins, etc. 

Exploding or burning the gas with oxygen or air and measuring both the change in volume and amount of waste gases formed by absorption. 

Sulphites react with molecular oxygen (or air) to give sulphates, a reaction catalysed by certain ions (for example Fe, Cu, arsenate(III) ion, AsO ) and inhibited by, for example, phenol, glycerol and tin(II) ions, Sn ... 

Oxidation. Acetaldehyde is readily oxidised with oxygen or air to acetic acid, acetic anhydride, and peracetic acid (see Acetic acid and derivatives). The principal product depends on the reaction conditions. Acetic acid [64-19-7] may be produced commercially by the Hquid-phase oxidation of acetaldehyde at 65°C using cobalt or manganese acetate dissolved in acetic acid as a catalyst (34). Liquid-phase oxidation in the presence of mixed acetates of copper and cobalt yields acetic anhydride [108-24-7] (35). Peroxyacetic acid or a perester is beheved to be the precursor in both syntheses. There are two commercial processes for the production of peracetic acid [79-21 -0]. Low temperature oxidation of acetaldehyde in the presence of metal salts, ultraviolet irradiation, or osone yields acetaldehyde monoperacetate, which can be decomposed to peracetic acid and acetaldehyde (36). Peracetic acid can also be formed directiy by Hquid-phase oxidation at 5—50°C with a cobalt salt catalyst (37) (see Peroxides and peroxy compounds). Nitric acid oxidation of acetaldehyde yields glyoxal [107-22-2] (38,39). Oxidations of /)-xylene to terephthaHc acid [100-21-0] and of ethanol to acetic acid are activated by acetaldehyde (40,41). 

Another method of manufacture involves the oxidation of 2-isopropylnaphthalene ia the presence of a few percent of 2-isopropylnaphthalene hydroperoxide/i)ti< 2-22-(y as the initiator, some alkaU, and perhaps a transition-metal catalyst, with oxygen or air at ca 90—100°C, to ca 20—40% conversion to the hydroperoxide the oxidation product is cleaved, using a small amount of ca 50 wt % sulfuric acid as the catalyst at ca 60°C to give 2-naphthalenol and acetone in high yield (70). The yields of both 2-naphthalenol and acetone from the hydroperoxide are 90% or better. 

The commercial product is a powder containing a minimum of 96% Na202 and approximately 20% active oxygen. It is made commercially by oxidizing the molten metal with either oxygen or air enriched in oxygen. Early industrial history (1) and manufacturing details (3) are available. Sodium... 

Potassium Superoxide. Potassium, mbidium, and cesium form superoxides, MO2, upon oxidation by oxygen or air. Sodium yields the peroxide, Na202 lithium yields the oxide, Li20, when oxidized under comparable conditions. Potassium superoxide [12030-88-5] KO2 liberates oxygen in contact with moisture and carbon dioxide (qv). This important property enables KO2 to serve as an oxygen source in self-contained breathing equipment. 

Zinc—Oxygen Cells. On the basis of reactants the zinc—oxygen or air system is the highest energy density system of all the alkaline rechargeable systems with the exception of the 2 Th reactants are cheap and abundant and therefore a number of attempts have been made to develop a practical rechargeable system. The reactions of this system are as follows ... 

Theoretical Oxygen and Air for Combustion The amount of oxidant (oxygen or air) just sufficient to burn the carbon, hydrogen, and sulfur in a fuel to carbon dioxide, water vapor, and sulfur dioxide is the theoretical or stoichiometric oxygen or air requirement. The chemical equation for complete combustion of a fuel is... 

Direct oxidation of C in a limited supply of oxygen or air yields CO in a free supply CO2... 

In processes involving the combustion of fuels, either pure oxygen or air is supplied in amounts greater than the stoichiometric requirements for complete combustion. The terms "theoretical air or theoretical oxygen are thus frequently encountered in combustion problems. The molar composition of dry air at atmospheric conditions [from International Critical Tables, Volume 1, p. 393 (1926)] ... 

The main route to ethylene oxide is oxygen or air oxidation of ethylene over a silver catalyst. The reaction is exothermic heat control is important ... 

Catalyst regeneration occurs by the reaction of thallium(I) chloride with copper(II) chloride in the presence of oxygen or air. The formed Cu(I) chloride is reoxidized by the action of oxygen in the presence of HCI ... 

Inorganic oxides are usually prepd by intimate contact between the element and oxygen or air. The reaction may be rapid and exothermic, as when finely divided pyrophoric materials ignite spontaneously in air or oxygen. Examples of these materials are iron, lead and phosphorus.-Or, the reaction may be slow as when iron oxidizes when exposed to ordinary moist air, or when aluminum oxidizes at the surface upon exposure to air. Much of the time oxidation re-... 

Nakajima and coworkers [30] observed that, in the presence of CuCl(OH).-TMEDA with oxygen or air as the oxidant, 2-naphthol 103a is transformed into l,l -bi-2,2 -naphthol 104a. A wide variety of substrates undergo oxidative coupUng in excellent yields (Scheme 28). It is worth noting that the reaction requires as little as 1 mol % of the catalyst. 

As is the case with pure bubble columns and gas-operated loop reactors, most bioreactors in technical use are aerated with oxygen or air. Reactors with pure surface aeration, such as roller bottles, shake flasks and small stirred reactors or special reactors with membrane aeration, are exceptions. The latter are used for the cultivation of cells and organisms which are particularly sensitive to shearing (see e. g. [28 - 29]). The influence of gas bubbles in increasing stress has been described in many publications (see e.g. [4, 27, 29, 30]). In principle it can be caused by the following processes ... 

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