Arsonic acids mechanism

With regard to the mechanism, Jacobson et td. proposed that the arsonic acid catalyst is transformed to the perarsonic add by hydrogen peroxide, the perarsonic add being the active oxidant (Scheme 4.5) [29]. This may well be the case for arsonic add-catalyzed epoxidations performed in 1,4-dioxane as solvent When using fluorinated alcohols as solvent, we believe that reversible ester formation is involved in the mechanism (Scheme 4.7). This assumption is based on ESI-MS studies of the reaction mixtures [23]. 

Cullen et al. (1994) have proposed a possible mechanism of arsenic methylation after the study in which arsenite, arsenate, monomethyl-arsonate or dimethylarsinic acid were added to the growth medium in the presence of the unicellular alga Polyphsa peniculus. Evidence of arsenic biomethylation by the micro-organism Apiotrichum humicola in the presence of L-methionine-methyl-d3 has come from the same laboratory (Cullen et al., 1995). Their findings point to the role of S-adenosylmethionine, or a related sulfonium compound as possible methyl donors. Arsenic biomethylation and biotransformation has also been demonstrated in a freshwater environment (Kuroiwa et al., 1994). 

Arsonated polystyrenes (9) in biphasic and triphasic systems may be used to catalyse the epoxidation of olefins by aqueous hydrogen peroxide. Yields with various olefins are uniformly high (58—100%) the mechanism of the epoxidation is similar to that of peroxycarboxylic acids (Scheme 9). 

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