Oxidations, free manganese ions

Oxidations Catalyzed by Free Manganese Ions in Solution. 52... 

Finally, it can be stated that many reactivity patterns of free radical ions are equally found in oxidative and reductive transformations involving initial inner-sphere ET, such as in reactions with samarium iodide [389], low valent titanium [390] and titanocene complexes [391], manganese(III) [392], and CAN [393]. 

Sulfur cycling is affected in a variety of ways, including UV photoinhibition of organisms such as bacterioplankton and zooplankton that affect sources and sinks of DMS and UV-initiated CDOM-sensitized photoreactions that oxidize DMS and produce carbonyl sulfide. Metal cycling also interacts in many ways with UVR via direct photoreactions of dissolved complexes and of metal oxides and indirect reactions that are mediated by photochemically-produced ROS. Photoreactions can affect the biological availability of essential trace nutrients such as iron and manganese, transforming the metals from complexes that are not readily assimilated into free metal ions or metal hydroxides that are available. Such photoreactions can enhance the toxicity of metals such as copper and can initiate metal redox reactions that transform non-reactive ROS such as superoxide into potent oxidants such as hydroxyl radicals. 

Sunda, W. G., D. W. Engel, and R. M. Thuotte (1978). Effect of chemical speciation on toxicity of cadmium to grass shrimp. Palaemonetes pugio Importance of free cadmium ion. Environ. Sci. Technol. 12, 409- 13. Takamatsu, T., M. Kawashima, andM. Koyama(1985). The role of Mn-rich hydrous manganese oxide in the accumulation of arsenic in lake sediments. Water Res. 19, 1029-1032. 

Oxidative free-radical degradation by hydroperoxides can be catalyzed by certain transition metal ions, especially those of copper, cobalt, and manganese. To reduce the rate of free radical formation, two classes of additives are used (1) organic phosphines, amines, and sulfides which catalyze the decomposition of the hydroperoxides to noiuadical products, and (2) metal-ion chelators (e.g., Ph-CH=NNH-CO-CO-NHN=CH-Ph). Tertiary phosphines are thus oxidized to phosphine oxides, tertiary amines to amine oxides, and sulfides to sulfoxides, e.g.,... 

The manganese ions in -i-3 oxidation states may be subject to a reversible disproportionation reaction or react first with the water molecules, and then with the reducing agent (Red) and monomer (M) with the formation of free radicals (M ), initiating the polymerization. 

Since a free radical is always formed in the reaction of an ion with a molecule during electron transfer, these redox systems are generators of free radicals. They are used for the initiation of reactions of radical polymerization, oxidation, and chlorination. For example, manganese ions initiate the chain oxidation of oxalate ions with chlorine in an aqueous solution. The process includes the following steps ... 

The oxidation of hydrocarbons, including hydrocarbon polymers, takes the form of a free-radical chain reaction. As a result of mechanical shearing, exposure of ultraviolet radiation, attack by metal ions such as those of copper and manganese as well as other possible mechanisms, a hydrocarbon molecule breaks down into two radicals... 

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