Manganese-catalyzed oxidation

Catalytic Oxidation for Straight-Chain Paraffinic Hydrocarbons. Synthetic fatty acids (SFA) are produced by Eastern European countries, Russia, and China using a manganese-catalyzed oxidation of selected paraffinic streams. The technology is based on German developments that were in use during World War II. The production volume in 1984 was estimated to be about 5.5 x ICf t/yr. The oxidation is highly exothermic and is carried out at about 105—125°C, mostly in continuous equipment. 

Without additives, radical formation is the main reaction in the manganese-catalyzed oxidation of alkenes and epoxide yields are poor. The heterolytic peroxide-bond-cleavage and therefore epoxide formation can be favored by using nitrogen heterocycles as cocatalysts (imidazoles, pyridines , tertiary amine Af-oxides ) acting as bases or as axial ligands on the metal catalyst. With the Mn-salen complex Mn-[AI,AI -ethylenebis(5,5 -dinitrosalicylideneaminato)], and in the presence of imidazole as cocatalyst and TBHP as oxidant, various alkenes could be epoxidized with yields between 6% and 90% (in some cases ionol was employed as additive), whereby the yields based on the amount of TBHP consumed were low (10-15%). Sterically hindered additives like 2,6-di-f-butylpyridine did not promote the epoxidation. 

As mentioned earlier, soluble salts of cobalt and manganese catalyze oxidation of cyclohexane by oxygen to cyclohexanol and cyclohexanone. Cyclohexanol and cyclohexanone are oxidized by nitric acid to give adipic acid. The oxidation by nitric acid is carried out in the presence of V5+ and Cu2+ ions. These reactions are shown by Eq. 8.8. Adipic acid is used in the manufacture of nylon 6,6. 

Fig. 1. Relative importance of various urban sulphate aerosol production mechanisms T = total sulfate A = H2SO4 condensation H = HjOj oxidation O = uncatalyzed oxygen oxidation Q = O3 oxidation F = iron catalyzed oxidation M = manganese catalyzed oxidation C = soot catalyzed oxidation.

In the presence of dioxygen, the carbon radical R- produced by reactions (201) and (202) ar transformed into alkylperoxy radicals ROO, reacts with Co or Mn species to regenerate th Co " or Mn " oxidants, and produce primary oxygenated products (alcohol, carbonyl compounds which can be further oxidized to carboxylic acids. This constitutes the basis of several Industrie processes such as the manganese-catalyzed oxidation of n-alkenes to fatty acids, and the cobal catalyzed oxidation of butane (or naphtha) to acetic acid, cyclohexane to cyclohexanol-on mixture, and methyl aromatic compounds (toluene, xylene) to the corresponding aromatic monc or di-carboxylic acids. ... 

Martin, L. R., and Hill, M. W., The effect of ionic strength on the manganese catalyzed oxidation of sulfur(IV). Atmos. Environ. 21, 2267 (1987b). 

T. Yamane, Flow Injection Determination of Hydrogen Peroxide by Means of the Manganese-Catalyzed Oxidation of Hydroxynaphthol Blue. Bunseki Kagaku, 33 (1984) E203. 

Whereas several catalytic methods are currently available for manganese-catalyzed epoxidation with aqueous H2O2, high turnover numbers for cis-dihydroxylation reactions so far have only been achieved with osmium compounds 161-165). However, manganese-catalyzed oxidation reactions have a few inherent advantages, such as the low price of the manganese salts and complexes and their non-toxic nature. 

Inoue and coworkers have reported the manganese-catalyzed oxidation of alcohols to ketones using persulfate as the terminal oxidant. Recrystallization of Oxone to give purified KHSO5 was found to be beneficial for in iroving the yield of the reaction (eq97). 

Bromide ions exert a synergetic effect on the cobalt and manganese catalyzed oxidation and also change the relative reactivities. For example, in the presence of added NaBr, cumene is 17 times more reactive than toluene (with cobalt acetate). 

Mechanisms in manganese-catalyzed oxidation of alkenes with H2O2 (pyridyl, quinoline, polypyridyl amine, trimethyltriazacyclononane, tet-... 

Manganese-Catalyzed Oxidative Cross-Coupling Reactions... 

Several chemocatalytic systems for sulfoxidation that employ other oxidants than hydrogen peroxide, molecular oxygen, or alkyl hydroperoxide have been reported. Manganese-catalyzed oxidation of sulfides with iodosobenzene (PhIO) using chiral Mn(salen) complexes was used to obtain chiral sulfoxides in up to 94% ee [71]. PhIO was also employed as the oxidant in sulfoxidations catalyzed by quaternary ammonium salts [72]. The use of cetyltrimethylammonium bromide (n-Ci6H33Me3N Br ) gave the best result, and with 5-10 mol% of this catalyst, high yields (90-100%) of sulfoxide were obtained from various sulfides. 

Manganese-Catalyzed Oxidation with Hydrogen Peroxide... 

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