1-Naphthylamine-4-sulfonic acid [84-86-6-A] C10H9NO3S
In a 1000 ml three-neck flask equipped with a KPG stirrer, Dimroth condenser, dropping funnel, and thermometer (up to 200 °C), melt 250 g of 1-naphthylamine and add 98 ml of concentrated sulfuric acid while stirring. The temperature of the mixture is raised to 180 °C, then 12.5 g of oxalic acid dihydrate is added. The oxalic acid keeps the mass porous and prevents oxidation. The mixture is heated further for 8 hours at 180 °C. It is very important to strictly adhere to the specified procedure and particularly the reaction temperatures. Failure to do so favors the formation of isomeric naphthylaminesulfonic acids and oxidation products. After the specified time, let the reaction mixture solidify and pulverize it. This is carefully washed with water in a Buchner funnel and sucked off. The purified product is dried in a vacuum desiccator. The yield is about 425 g of pure 1-naphthylamine-4-sulfonic acid. The product is used in the manufacture of many azo dyes, such as Congo red.
Source: Fierz-David, Blangey - Fundamental Processes of Dye Chemistry, Interscience, New York, 1949
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Last updated: 20/09/2005
Other names: α-Naphthylamine-4-sulfonic acid; 4-Amino-1-naphthalenesulfonic acid; 1-Amino-4-sulfonaphthalene; NSC 4155; Naphthionic acid; Piria acid