Arsinic acids mechanism

The esters of arsinic acid are more thermally labile, often resinifying on distillation. However, catalysed pyrolyses using alkyl halides, salts or mineral acids afford useful yields ca 50%) of arsenic(III) esters . The mechanism is considered to involve the pyrolysis of an alkoxyarsonium salt 7 is formed with the catalyst. 

The mechanism involves initial formation of an acetylated or phosphorylated cation, which reacts with a carbanion to form a salt that is strongly acidic because of its substituent electron-withdrawing groups. This salt is hence readily converted into an ylide by loss of a proton, whose removal is assisted by the acetic anhydride or triethylamine (see equation 27). As with method B the arsine oxide method is limited to the preparation of stable ylides, since its success depends upon the acidity of the methylene compound. Almost all examples of this method have utilized triphenylarsine oxide tri-w-butylarsine oxide has been used in triethylamine but gave only intractable products in acetic anhydride In a modification of this method, an ylide has been prepared by reaction of acetoacetanilide with diacetoxytriphenylarsorane, the latter compound having been prepared from triphenylarsine and lead tetra-acetate. ... 

The mechanisms of the oxidation of phosphines and arsines by chromium(VI) have been examined both in solution and on a diatomite support. Kinetic parameters are presented for both supported and solution reactions. A ruthenium complex of 1,4,8,1 l-tetramethyl-l,4,8,ll-tetraazacyclotetradecane has been utilized to oxidize triphenylphosphine in acetonitrile. Although a limited temperature range was utilized, a AH value of 8.7 0.8 kcal mor and a A5 value of -20 2 cal K mor were calculated. The secondary phosphine oxides, HP(0)R (R = n-butyl, isobutyl, cyclohexyl) and 9H-9-phosphabicyclononane-9-oxide, react with cobaltocene to yield dihydrogen and cobalt(I) compounds. With the less bulky phosphorus ligands at elevated temperatures trinuclear cobalt(III, II) complexes may be obtained. Arsenious acid may be utilized to catalyze the oxygen atom... 

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