Nitronaphthalenesulfonic acids

Sulfonation. Sulfonation of naphthalene with sulfuric acid produces mono-, di-, tri-, and tetranaphthalenesulfonic acids (see Naphthalene derivatives), ah of the naphthalenesulfonic acids form salts with most bases. Naphthalenesulfonic acids are important starting materials in the manufacture of organic dyes (15) (see Azo dyes). They also are intermediates used in reactions, eg, caustic fusion to yield naphthols, nitration to yield nitronaphthalenesulfonic acids, etc. 

Nitronaphthalenesulfonic Acids. Nitronaphthalenesulfonic acids can be obtained either by the sulfonation of 1-nitronaphthalene or by the nitration of 1- or 2-naphthalenesulfonic acid. Thus the sulfonation of 1-nitronaphthalene with oleum at ca 25°C gives mainly 5-nitro-l-naphthalenesulfonic acid/77521-00-5]. The mononitration of 1-naphthalenesulfonic acid gives mainly 5- and 8-nitro-l-naphthalenesulfonic acid/717-41-9] and mononitration of 2-naphthalenesulfonic acid gives mainly 5-nitro-2-naphthalenesulfonic acid [86-69-1] and 8-nitro-2-naphthalenesulfonic acid [18425-74-6]. These... 

Sulfonation of a-naphthylamine always gives mixed sulfonic acids, the first sulfo group entering at position 4, 5, or 6. Most of the sulfonic acids of ot-naphthylamine are, however, not prepared by sulfonation of this amine but rather by other methods, such as reduction of nitronaphthalenesulfonic acids. 

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