Bart reaction Scheller modification

Bart reaction. (Scheller modification Star-key modification). Formation of aromatic arsonic acids by treating aromatic diazonium compounds with alkali arsenites in the presence of cupric salts or powdered silver or copper in the Scheller modification, primary aromatic amines are diazotized in the presence of arsenious chloride and a trace of cuprous chloride. 

The success of the Bart reaction when applied to nuclear- substituted anilines is often much affected by the pH of the reaction-mixture. Furthermore, the yields obtained from some m-substituted anilines, which under the normal conditions are usually low, arc considerably increased by the modifications introduced by Scheller, and by Doak, in which the diazotisation is carried out in ethanolic solution followed by reaction with arsenic trichloride in the presence of a cuprous chloride or bromide catalyst. 

It is pertinent to mention here that the success of the Bart Reaction when applied to nuclear-substituted anilines e.g., m-substitued anilines) is invariably effected by the prevailing pH of the reaction medium. Scheller (1992) and Doak et al. (1946) suggested certain modifications whereby the yields obtained from certain m-substituted anilines, which under the usual conditions of reactions are very low, could be enhanced considerably by carrying out... 

This reaction was first reported by Bart in 1910. It is the synthesis of arylarsenic acids from aromatic diazonium compounds with alkali arsenites in the presence of cupric salts, powdered silver, or copper. Therefore, this reaction is generally known as the Bart reaction. In addition, the reaction between aromatic diazonium and arsenious chloride in the presence of trace amounts of cuprous chloride is referred to as the Scheller modification. Besides the Scheller modification, the Sakellarios modification is the reaction between sulfanilamide and phenyldisodium arenite. ... 

A few modifications have been developed for the Bart reaction, including the Scheller modification and the Sakellarios modification. The most useful and famous one is the Scheller modification. 

An important modification of the original Bart procedure was made by Scheller who diazotized primary amines, dissolved in alcohol or glacial acetic acid, in the presence of arsenic trichloride and found that better yields of arsonic acids could sometimes be obtained, particularly if the amine carried negative substituents in the meta position. The method has been slightly modified 140). The Scheller reaction has recently been used to prepare arsonic acids of 3-nitro-4-fluorobenzene and 2,5-dimethylpyridine 141, 142), and to prepare a number of arsinic acids such as (CeHs)[4,3-CH3(N02)C6H3]As02H by the reaction 143)... 

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