Sulfanilic acid

Structural formula
General
Surname	Sulfanilic acid
other names	4-aminobenzenesulfonic acid 4-aminobenzenesulfonic acid ( IUPAC ) 4-aminobesilate Aniline-4-sulfonic acid p -aminobenzenesulfonic acid p -anilinesulfonic acid
Molecular formula	C 6 H 7 NO 3 S
Brief description	white, crystalline solid
External identifiers / databases
CAS number 121-57-3 (anhydrous) 6101-32-2 (monohydrate) EC number 204-482-5 ECHA InfoCard 100.004.075 PubChem 8479 ChemSpider 8166 Wikidata Q253746
properties
Molar mass	173.19 g mol −1
Physical state	firmly
density	1.485 g cm −3 (25 ° C)
Melting point	Decomposes at 288 ° C
solubility	slightly soluble in water: 10 g l −1 (20 ° C)
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary Caution H and P phrases H: 319-315-317 P: 280-302 + 352-305 + 351 + 338
Toxicological data	12300 mg kg −1 ( LD 50 ,  rat ,  oral ) 100 mg l −1 ( LC 50 ,  fish , 96 h , median value)
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Sulphanilic acid is the common name for 4-aminobenzenesulphonic acid . Aminobenzenesulfonic acids are important industrial intermediates for the synthesis of organic, water-soluble dyes. Due to the high acidity of the sulfonic acid function, in contrast to aminocarboxylic acids, their isoelectric point (IEP) is acidic.

synthesis

It is obtained by heating sulfuric acid with aniline to 190 ° C. A sulfonic acid function is thus bonded to the benzene ring in an electrophilic substitution in the p -position to the amino group.

An upstream equilibrium of the autoprotolysis of sulfuric acid produces H ₃ SO ₄ ⁺ ions:

${\displaystyle \mathrm {2\ H_{2}SO_{4}\rightleftharpoons \ H_{3}SO_{4}^{+}\ +\ HSO_{4}^{-}} }$

These can split off water and HSO ₃ ^{+ is formed} as an electrophile, which can attack the ring in the ortho or para position to the protonated amino group.

Physical Properties

The flash point is> 200 ° C, the ignition temperature> 400 ° C.

use

Sulphanilic acid is required for the production of Lunge's reagent for the detection of nitrite or nitrate .

Reaction scheme for the reaction of the lung reagent with nitrite. By adding 2 to 3 drops of lung I and II, the sulfanilic acid ( 1 ) first forms a diazonium salt  ( 2 ), which further reacts with 1-naphthylamine  ( 3 ) to form an azo dye  ( 4 ) and quickly turns the solution red .

It is also used in the synthesis of azo dyes such as methyl orange or orange II . It is also a primary substance according to the Pharmacopoeia .

Sulphanilic acid is of particular importance as a starting material for the production of chemotherapeutic agents from the group of sulphonamides . Sulphanilic acid itself has no significant effect against bacteria, as it can hardly penetrate the membrane of the microorganisms due to its high polarity.

Individual evidence

1. ↑ ^{a b c d e f g h i} entry to sulfanilic acid in the GESTIS database of IFA , retrieved on December 22, 2019(JavaScript required) .
2. ↑ Entry on Sulphanilic acid in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
3. ^ SY Hwang, DA Berges, JJ Taggart, C. Gilvarg: Portage transport of sulfanilamide and sulfanilic acid. In: Journal of medicinal chemistry. Volume 32, Number 3, March 1989, pp. 694-698, PMID 2645404 .

Web links

Wiktionary: sulfanilic acid  - explanations of meanings, word origins, synonyms, translations