Arsinic acids, aromatic, preparation

The Bart reaction is successful with a wide variety of aromatic and heterocycHc amines. A variation in which an aromatic amine, in the presence of arsenic trichloride, is dia2oti2ed in an organic solvent (the ScheUer reaction) has also found wide appHcation. Both arsonic and arsinic acids can be prepared by the ScheUer reaction which often gives better yields than the Bart reaction with electron-attracting substituents on the aromatic ring. For the commercial preparation of 4-aminophenylarsonic acid [98-50-0] (arsaniUc acid), C HgAsNO, and 4-hydroxyphenylarsonic acid [98-14-6] C H AsO, the Bnchamp reaction is used ... 

The Preparation op Aromatic Arsonic and Arsinic Acids by the Bart, Bechamp, and Rosenmund Reactions—Cliff S. Hamilton and Jack F. Morgan 415... 

It has already been stated that Bart used catalysts in his reaction, in order to eliminate the diaze-nitrogen at low temperatures and thus decrease the formation of by-products. In Schmidt s method, in addition to non-arseuated aromatic derivatives, arsenated derivatives may also occur as by-products. In the case of the preparation of phenyl-arsinic acid, the by-product is diphenylyl-4-arsinic acid, CgH4.Ph. AsO(OH)2, and the presence of such a derivative can only be accounted for on the assumption that one of the hydrogen atoms of tire benzene nucleus becomes labile at the moment when the replacement of the diazo-group by the arsinic acid grouping takes place. 

This acid has a special interest for two reasons firstly, it was the first aromatic arsenical to be produced, although it was not recognised as such at the time secondly, its so um salt, Atoxyl, has proved of great value in medicine. Consequently, many attempts have been made to prepare this arsinic acid, but none seem to have been very successful as far as the yield is concerned. The following preparation is that due to Cheetham and Schmidt ... 

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