Metanilic acid derivatives

The Bechamp method can also be used in reducing the nitro derivatives of sulfonic acids. A typical example being the manufacture of metanilic acid and related substances [11]. 

The amido-sulphonic adds, since they are derivatives of a primary amine, may like them be diazotised by tile action of nitrous add upon tins fact depends their great technical importance. If the diazo-com-pounds thus obtained are combined with amines or phenols, azo dyes are formed which contain the sulphonic add group, and in the form of their alkali salts are soluble in water. Sulplianilic acid particularly, and its isomer, metanilic add, obtained by the reduction of m-nitro-benzenesulphonic add, as well as the numerous mono- and poly-sul-phonic acids derived from a and / naphthyl amines, find extensive technical application in the manufacture of azo dyes-... 

Benzene at 110°C with H2O2 and I2 gives the /7-diiodo-derivative [266]. 2-Naphthol can be 1-iodinated under milder conditions in ethanol [267]. Industrial applications of iodination with H2O2 include manufacture of 2,6-diodo-4-nitrophenol (anthelminthic drug) [268] and of 2-iodo-4-chloro-metanilic acid (optical brightener intermediate) [269]. 

Occasionally, metanil yellow (acid yellow 36) has been reported as a cause of contact allergy due to leather products. A young man suffered from a foot eczema after wearing industrial leather protective shoes. On patch testing he reacted to metanil yellow, which was present in the leather of the inners and stiffeners. He also reacted to the leather itself, p-aminonazobenzene, PPD and its derivatives (Ancona et al. 1982). A woman working in a leather shop developed a contact allergy to metanil yellow, probably by contact with a brown leather portfolio. She also reacted to p-aminoazobenzene and p-aminodiphenyl-amine in the patch test (Hausen 1994). 

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