Sulfanilic acid

Sulfanilic acid (4-aminobenzenesulfonic acid) is an organic compound with the formula H₃NC₆H₄SO₃. It is an off-white solid. It is a zwitterion, which explains its high melting point. It is a common building block in organic chemistry.^[4]

Sulfanilic acid

Names
Preferred IUPAC name 4-Aminobenzene-1-sulfonic acid[1]
Other names 4-Aminobenzenesulfonic acid p-Aminobenzenesulfonic acid Sulfanilic acid (not retained[1])
Identifiers
CAS Number	121-57-3 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:27500 N
ChEMBL	ChEMBL1566888
ChemSpider	8166
ECHA InfoCard	100.004.075
EC Number	204-482-5
Gmelin Reference	101735
KEGG	101735 N
PubChem CID	8479
UNII	434Z8C2635 Y
UN number	2585
CompTox Dashboard (EPA)	DTXSID6024464
InChI InChI=1S/C6H7NO3S/c7-5-1-3-6(4-2-5)11(8,9)10/h1-4H,7H2,(H,8,9,10) Key: HVBSAKJJOYLTQU-UHFFFAOYSA-N InChI=1/C6H7NO3S/c7-5- 1-3-6(4-2-5)11(8,9)10/h1-4H, 7H2,(H,8,9,10)/f/h8H
SMILES OS(=O)(=O)c1ccc(N)cc1
Properties
Chemical formula	C6H7NO3S
Molar mass	173.19
Density	1.485
Melting point	288 °C (550 °F; 561 K)
Solubility in water	12.51 g/L
Acidity (pKa)	3.23 (H2O)[2]
Hazards
GHS labelling:[3]
Pictograms
Signal word	Warning
Hazard statements	H315, H317, H319
Precautionary statements	P261, P264, P264+P265, P272, P280, P302+P352, P305+P351+P338, P321, P332+P317, P333+P317, P337+P317, P362+P364, P501
Related compounds
Related sulfonic acids	Benzenesulfonic acid p-Toluenesulfonic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Synthesis

Sulfanilic acid can be produced by sulfonation of aniline with concentrated sulfuric acid.^[5] 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.^[6][7] 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.^[8][9]

Applications

As the compound readily forms diazo compounds, it is used to make dyes and sulfa drugs.^[4] 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.^[10]

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.^[11] It is produced by reduction of some azo dyes.^[12]

Derivatives

• Methyl orange (azo coupling with dimethylaniline)
• Acid orange 7 (azo coupling with 2-naphthol)^[13]
• Chrysoine resorcinol (azo coupling with resorcinol)

See also

• Orthanilic acid
• Metanilic acid
• Sulfanilamide

References

1. Favre, Henri A.; Powell, Warren H., eds. (2014). Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: Royal Society of Chemistry. p. 789. doi:10.1039/9781849733069-FP001. ISBN 9780854041824. OCLC 1077224056. The name 'sulfanilic acid' is not retained.
2. Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press. p. 5–88. ISBN 978-1498754286.
3. "Sulfanilic acid". pubchem.ncbi.nlm.nih.gov.
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. Bamberger, Eug.; Kunz, Jac. (May 1897). "Umlagerung von Sulfonsäuren. (II.)". Berichte der Deutschen Chemischen Gesellschaft. 30 (2): 2274–2277. doi:10.1002/cber.189703002211.
7. Illuminati, Gabriello (June 1956). "A Reinvestigation of the Role of Phenylsulfamic Acid in the Formation of Aminobenzenesulfonic Acids". Journal of the American Chemical Society. 78 (11): 2603–2606. doi:10.1021/ja01592a075.
8. Spillane, W.J.; Scott, F.L. (January 1967). "Radiosulphur studies on the rearrangement of phenylsulphamic acid to sulphanilic acid". Tetrahedron Letters. 8 (14): 1251–1253. doi:10.1016/S0040-4039(00)90678-6.
9. Scott, F.L.; Spillane, W.J. (January 1967). "The isomerization of orthanilic acid to sulphanilic acid in the presence of sulphuric acid-S35". Tetrahedron Letters. 8 (28): 2707–2711. doi:10.1016/S0040-4039(01)89979-2.
10. G. H. Jerffery; J. Bassett; J. Mendham; R. C. Denney (1989). "Colorimetry and Spectrophotometry". Vogel's Textbook of Quantitative Chemical Analysis, 5th Edition. Longman. p. 702. ISBN 0-582-44693-7.
11. Holm, John V.; Ruegge, Kirsten.; Bjerg, Poul L.; Christensen, Thomas H. (1995). "Occurrence and Distribution of Pharmaceutical Organic Compounds in the Groundwater Downgradient of a Landfill (Grindsted, Denmark)". Environmental Science & Technology. 29 (5): 1415–1420. Bibcode:1995EnST...29.1415H. doi:10.1021/es00005a039. PMID 22192041. S2CID 2994687.
12. Nam, S. (2000). "Reduction of azo dyes with zero-valent iron". Water Research. 34 (6): 1837–1845. Bibcode:2000WatRe..34.1837N. doi:10.1016/S0043-1354(99)00331-0.
13. Klaus Hunger; Peter Mischke; Wolfgang Rieper; Roderich Raue; Klaus Kunde; Aloys Engel (2005). "Azo Dyes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a03_245. ISBN 978-3527306732..