Transition metal peroxides alcohols

Hock-cleavage, hpid oxidation, 946 HOI see Hypoiodous acid HomoaUyhc alcohols, transition metal peroxide oxidation, 1089-94... 

Pyridine, methyltrioxorhenium hgands, 460-1 Pyridine-2,6-dicarboxylate (dipic), transition metal peroxides, 1060, 1061 Pyridinium dichromate, alcohol oxidation, 787-8... 

Alcohol autoxidation is carried out in the range of 70—160°C and 1000—2000 kPa (10—20 atm). These conditions maintain the product and reactants as Hquids and are near optimum for practical hydrogen peroxide production rates. Several additives including acids, nitriles, stabHizers, and sequestered transition-metal oxides reportedly improve process economics. The product mixture, containing hydrogen peroxide, water, acetone, and residual isopropyl alcohol, is separated in a wiped film evaporator. The organics and water are taken overhead and further refined to recover by-product acetone and the... 

Lewis acids such as SnCl4 also catalyze the reaction, in which case the species that adds to the alkenes is H2C —O— SnC. Montmorillonite KIO clay containing zinc(IV) has been used to promote the reaction. The reaction can also be catalyzed by peroxides, in which case the mechanism is probably a free-radical one. Other transition metal complexes can be used to form allylic alcohols. A typical example is. ... 

Several compounds of tungsten, which is a transition metal closely related to molybdenum, are able to catalyze the selective oxidation of secondary alcohols with hydrogen peroxide as secondary oxidant. These include tris(cetylpyridinium) 12-tungstophosphate,33 peroxotungstopho-sphate (PCWP)34 and Na2W04 in the presence of a phase transfer catalyst.35 Tungstophosphoric acid is able to catalyze the selective oxidation of secondary alcohols in the presence of ferric nitrate as secondary oxidant.36... 

Hydrogen peroxide and peroxycarboxylic acids (RCO3H) are normally relatively stable, but as mentioned above they can be rendered unstable by a wide variety of contaminants, particularly at excessively high temperatures. Cleanliness, good housekeeping and proper storage are therefore essential. The major contaminants that cause decomposition are combustible organic materials (e.g. cotton, wool, paper) or metals, particularly transition metals and their salts (Table 1.7).50 Alcohol thermometers or stainless steel thermocouples... 

Metals that are capable of 2e redox changes, typically main group elements and 4d and 5d transition metals, can give heterolysis of a peroxide to form a diamagnetic oxidant that may avoid the radical pathways seen in the case of equation (14-15). O atom transfer to the substrate is possible in this way. Sharpless epoxidation provides an excellent example. In this case rBuOOH is the primary oxidant, Ti(i-OPr)4 is the catalyst precursor and a tartrate ester is the ligand that induces a high ee in the epoxy alcohol formed from an allylic alcohol. This reaction has been successfiiUy developed on an industrial scale. 

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