Manganese catalyzed reaction

While many important details of the iron- and manganese-catalyzed reactions are yet to be explored, the common features of the corresponding mechanisms are well established and also applicable in the presence of other catalysts. Thus, the formation of the SO5, SO4 and HSO5 intermediates was reported in all of the free-radical type reactions. These species are very reactive oxidants and this explains the apparent... 

Peracetic acid decomposition kinetics in the presence of cobalt or copper acetates were studied in the same apparatus used for the manganese-catalyzed reaction. However, in these studies it was used as a batch reaction system. The reactor was charged with peracetic acid (ca. 0.5M in acetic acid) and allowed to reach the desired temperature. At this time the catalyst (in acetic acid) was added. Samples were withdrawn and quenched with potassium iodide at measured time intervals. 

Peracetic Acm-AcErALDEHYDE Reaction. The cobalt- and manganese-catalyzed reactions of peracetic acid with acetaldehyde were studied by a continuous flow technique (9). Peracetic acid (0.15M in acetic acid) and acetaldehyde-catalyst solutions were metered through rotameters to a mixing T (standard 0.25-inch stainless steel Swagelok T) and... 

The Mn(II)/Mn(III) system has not been studied in as much detail as cobalt, but the principles discussed above are also probably applicable to the manganese-catalyzed reactions ... 

Via hydrocohaltation and other cobalt- and manganese-catalyzed reactions... 

Balasubramanian et al. in 1988 [75] reported first illustration of the inclusion of the BZ reaction into an AOT reverse micelle system. The coupling of an oscillating chemical reaction which shows spatial and temporal phenomenon relevant to biological systems was the main motivation for this study. In manganese-catalyzed reaction system oscillatory behavior was monitored for this particular case. Vanag et al. [76] has been studied the BZ-AOT reaction in a great detail emphasized in particular on the formation of non-equilibrium chemical patterns. 

Aziridination of Alkenes. Iron- and manganese-porphyrin corrqilexes catalyze the reaction of PhI=NTs with alkenes to form the corresponding fV tosylaziridines. Mn(TPP)Cl is generally a better catalyst than the analogous iron complex, affording 80% of the aziridine from the reaction with styrene (eq 11). Good yields are also obtained in the manganese-catalyzed reactions with 1,1-and l,2-diphenylethylenes. Yields of aziridines derived from aliphatic alkenes remain low and are complicated by the formation of allylic amines. 

This manganese-copper-catalyzed conjugate addition reaction compares favorably with the classical copper-catalyzed reaction. The two reactions are easily and similarly carried out under mild conditions, but the first one gives higher yields. This difference, already observed in the case of p-monosubstituted o,p-ethylenic ketones, is especially noticeable with p,p-disubstituted or [Pg.70]

The superoxide anion radical and hydrogen peroxide are not particularly harmful to cells. It is the product of hydrogen peroxide decomposition, the hydroxyl radical (HO ), that is responsible for most of the cytotoxicity of oxygen radicals. The reaction can he catalyzed hy several transition metals, including copper, manganese, cohalt, and iron, of which iron is the most ahimdant in the human body (Reaction 2 also called the Fenton reaction). To avoid iron-catalyzed reactions, iron is transported and stored chiefly as Fe(III), although redox active iron can be formed in oxidative reactions, and Fe(III) can be reduced by semiquinone radicals (Reaction 3). 

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. 

The results obtained in the manganese-catalyzed epoxidation reactions of various olefins are shown in Table 24. 

In subsequent research, it turned out that two-state reactivity can also provide a concept for the understanding of oxidation reactions way beyond the scope of gas-phase ion chemistry and can actually resolve a number of existing mechanistic puzzles. In enzymatic oxidations involving cytochrome P450, for example, changes in spin multiplicity appear to act as a kind of mechanistic distributor for product formation [27-29], and in the case of manganese-catalyzed epoxidation reactions, two-state scenarios have been put forward to account for the experimentally observed stereoselectivities [30-32], Two-state reactivity is not restricted to oxidation reactions, and similar scenarios have been proposed for a number of other experimentally studied reactions of 3d metal compounds [33-37]. Moreover, two-state scenarios have recently also been involved in the chemistry of main group elements [38]. The concept of two-state reactivity developed from the four-atomic system FeO /H2... 

Figure F shows some acetylene insertion reactions. These, too, are similar to the olefin insertion reactions. The manganese and cobalt hydrocarbonyls again add. Chloronickelcarbonyl hydride, which I believe is an intermediate in many of the nickel carbonyl-catalyzed reactions, adds to olefins. Diborane and the aluminum hydrides also add.

The enzyme that catalyzes reaction 7 has been solubilized, 4" 141 and purified141 2000-fold. The enzyme activity is dependent on manganese ions. The enzymes catalyzing reactions 5 and 6 have not yet heen solubilized, purified, or separated, and, therefore, the substrate specificities indicated remain speculative. 

These processes are catalyzed by bacteria and probably involve both inorganic and organic iron and manganese species (22). They may also be strongly controlled by microbial competition between Fe(III) and sulfate-reducing bacteria (27). Associated with these reduction reactions is the reduction of residual sulfate (produced in the oxic zone by bacterially catalyzed reactions) similar to eq 7 (21). 

Disubstituted alkcncs undergo a manganese(m) catalyzed reaction with (2-aryl-2-oxoethyl)malonates 208 to afford tetrasubstituted 3,4-dihydropyrans the formation of a y-lactone side-product is observed in some instances (Equation 98) <2004TL3373>. 

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