O Nitrophenylarsonic acid

By means of this method, o-nitrophenylarsonic acid was prepared in a yield of 86% as compared with a yield of only 60% by the original Bart process. According to Schmidt, the proportion of by-products, especially the parent hydrocarbon (benzene in the illustration), increases with higher alkalinity. In acid solution the yields are low unless the aromatic diazo compounds contain strongly negative substituents, such as nitro groups, in the ortho and para positions (as in 2,4-dinitrobenzenediazo-nium chloride, for example). 

In the reduction of o-nitrophenylarsonic acid with the aid of ferrous sulfate, ammonia is not a strong enough base to decompose the iron salt of the amino arsomc acid, and sodium hydroxide must be used. 

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