Sulfanilic acid

Chemical compound From Wikipedia, the free encyclopedia

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 compared to the related compounds aniline and benzenesulfonic acid.[how?] It is a common building block in organic chemistry.[4]

Quick facts Names, Identifiers ...
Sulfanilic acid
Skeletal formula of sulfanilic acid
Ball-and-stick model of the sulfanilic acid zwittrion
Names
Preferred IUPAC name
4-Aminobenzene-1-sulfonic acid[1]
Other names
4-Aminobenzenesulfonic acid
p-Aminobenzenesulfonic acid
Sulfanilic acid (not retained[1])
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.004.075 Edit this at Wikidata
EC Number
  • 204-482-5
101735
KEGG
UNII
UN number 2585
  • 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
  • OS(=O)(=O)c1ccc(N)cc1
Properties
C6H7NO3S
Molar mass 173.19
Density 1.485
Melting point 288 °C (550 °F; 561 K)
12.51 g/L
Acidity (pKa) 3.23 (H2O)[2]
Hazards
GHS labelling:[3]
GHS07: Exclamation mark
Warning
H315, H317, H319
P261, P264, P264+P265, P272, P280, P302+P352, P305+P351+P338, P321, 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).
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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

See also

References

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