Orthanilic acid

Structural formula
General
Surname	Orthanilic acid
other names	2-aminobenzenesulfonic acid 2-aminobesilate Aniline-2-sulfonic acid o -aminobenzenesulfonic acid o -anilinesulfonic acid
Molecular formula	C 6 H 7 NO 3 S
Brief description	light brown, crystalline solid
External identifiers / databases
CAS number 88-21-1 EC number 201-810-9 ECHA InfoCard 100.001.646 PubChem 6926 ChemSpider 6660 Wikidata Q2031743
properties
Molar mass	173.19 g mol −1
Physical state	firmly
density	3.05 g cm −3 (23 ° C)
Melting point	315 ° C
solubility	soluble in water
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 314 P: 305 + 351 + 338-310-280-301 + 330 + 331-303 + 361 + 353
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Orthanilic acid is the common name for 2-aminobenzenesulfonic 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.

Manufacturing

Benzenesulphonic acid is nitrated to a mixture of 2- and 3-nitrobenzenesulphonic acid and the o-isomer (2-nitrobenzenesulphonic acid) is reduced to orthanilic acid after isomer separation via the magnesium salts with iron in an acidic medium .

use

Orthanilic acid is a widely used diazo component in the manufacture of azo dyes. The sulfonic acid group in the ortho steric shields and protects the azo bridge. The result is dyes with increased in-use fastness properties (compared to metanilic acid or sulfanilic acid as diazo components).

Individual evidence

1. ↑ ^{a b} Orthanilic acid data sheet at Acros, accessed on February 19, 2010.
2. ↑ ^{a b c d} Entry on 2-aminobenzenesulphonic acid in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .