Sulfanilic acid

Synthesis

Sulfanilic acid can be produced by sulfonation of aniline with concentrated sulfuric acid. This proceeds via phenylsulfamic acid; a zwitterion with a N-S bond. Eugen Bamberger originally proposed a mechanism involving a series of intramolecular rearrangements, with phenylsulfamic acid forming orthanilic acid, which rearranged to sulfanilic acid on heating. Subsequent radiosulphur studies showed that the process is intermolecular, with the phenylsulfamic acid desulfating to generate sulfur trioxide, which then reacts with aniline at the para position in manner similar to a Bamberger rearrangement.

:[[File:Synthetic route of sulfanilic acid from aniline.png|none|600px]]

Applications

As the compound readily forms diazo compounds, it is used to make dyes and sulfa drugs. This property is also used for the quantitative analysis of nitrate and nitrite ions by diazonium coupling reaction with N-(1-Naphthyl)ethylenediamine, resulting in an azo dye, and the concentration of nitrate or nitrite ions were deduced from the color intensity of the resulting red solution by colorimetry.{{cite book

:[[File:Formation of the diazonium derivative of sulfanilic acid.png|200px]]

It is also used as a standard in combustion analysis and in the Pauly reaction.

Environmental aspects

Reflecting its wide use, sulfanilic acid is found in the leachates of landfills. It is produced by reduction of some azo dyes.

Derivatives

• Methyl orange (azo coupling with dimethylaniline)
• Acid orange 7 (azo coupling with 2-naphthol)
• Chrysoine resorcinol (azo coupling with resorcinol)

References

References

1. (2014). "Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book)". [[Royal Society of Chemistry]].
2. (2016). "CRC Handbook of Chemistry and Physics". [[CRC Press]].
3. "Sulfanilic acid".
4. "Sulphanilic acid". ''A Dictionary of Chemistry''. Oxford University Press, 2000. Oxford Reference Online. Oxford University Press.
5. Siegfried Hauptmann: ''Organische Chemie'', 2nd Edition, VEB Deutscher Verlag für Grundstoffindustrie, Leipzig, 1985, p. 511, {{ISBN. 3-342-00280-8.
6. (May 1897). "Umlagerung von Sulfonsäuren. (II.)". Berichte der Deutschen Chemischen Gesellschaft.
7. (June 1956). "A Reinvestigation of the Role of Phenylsulfamic Acid in the Formation of Aminobenzenesulfonic Acids". Journal of the American Chemical Society.
8. (January 1967). "Radiosulphur studies on the rearrangement of phenylsulphamic acid to sulphanilic acid". Tetrahedron Letters.
9. (January 1967). "The isomerization of orthanilic acid to sulphanilic acid in the presence of sulphuric acid-S35". Tetrahedron Letters.
10. (1995). "Occurrence and Distribution of Pharmaceutical Organic Compounds in the Groundwater Downgradient of a Landfill (Grindsted, Denmark)". Environmental Science & Technology.
11. (2000). "Reduction of azo dyes with zero-valent iron". Water Research.
12. (2005). "Azo Dyes".