H-acid

Structural formula
General
Surname	H-acid
other names	4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid ( IUPAC ); 8-amino-1-hydroxy-3,6-disulfonic acid naphthalene; 8-amino-1-naphthol-3,6-disulfonic acid;
Molecular formula	C 10 H 9 NO 7 S 2
External identifiers / databases
EC number	201-975-7
ECHA InfoCard	100.001.796
PubChem	7009
ChemSpider	6742
Wikidata	Q906915
properties
Molar mass	319.31 g mol −1
Physical state	firmly
safety instructions
GHS labeling of hazardous substances Monosodium salt	no GHS pictograms
	no GHS pictograms
H and P phrases	H: no H-phrases
	P: no P-phrases
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

H-acid is the common name for 4-amino-5-hydroxynaphthalene-2,7-disulfonic acid . The compound is one of the letter acids - these are important industrial intermediates in the synthesis of organic, water-soluble dyes .

H-acid is produced, marketed and used as a monosodium salt.

Manufacturing

The production of H-acid is a multi-stage process in which firstly naphthalene 1 with oleum sulfonated is. The naphthalene-1,3,6-trisulfonic acid 2 is then nitrated to give 1-nitro-3,6,8-trisulfonic acid 3 and this is reduced with iron to give 1-aminonaphthalene-2,6,8-trisulfonic acid (T-acid) 4 . In the last step, the 1-aminonaphthalene-2,6,8-trisulfonic acid isolated between them is reacted with sodium hydroxide solution under pressure and the H-acid 5 formed is isolated as the monosodium salt. The yield in the last step is 70-72%. By-products include 3-hydroxy-8-aminonaphthalene-1,6-disulfonic acid (W acid) and chromotropic acid . Alternatively, 1-nitro-3,6,8-trisulfonic acid can also be catalytically hydrogenated to 1-amino-3,6,8-trisulfonic acid .

use

H-acid is a widely used coupling component in the manufacture of azo dyes . Coupling to H-acid can take place twice, on the one hand acidic ( pH value of the coupling solution <3) in the amine ring (red chromophores ), then basic in the phenol ring (blue chromophores). Primary bisazo dyes are accessible as bifunctional coupling components with the H-acid.

Individual evidence

↑ ^a ^b Entry on sodium hydrogen 4-amino-5-hydroxynaphthalene-2,7-disulfonate in the GESTIS substance database of the IFA , accessed on October 9, 2018(JavaScript required) .
↑ External identifiers of or database links for sodium 4-amino-5-hydroxy-7-sulfo-2-naphthalene sulfonate : CAS number: 5460-09-3, EC number: 226-736-4, ECHA - InfoCard: 100.024.306 , GESTIS substance database : 494656 , PubChem : 23664361 , ChemSpider : 20310 , Wikidata : Q72439883 .
↑ ^a ^b Patent DE2732266 : Process for the production of 1-amino-8-naphthol-3,6-disulfonic acid (H-acid). Registered on July 16, 1977 , published on February 1, 1979 , applicant: Bayer AG, inventor: Willi Schößler, Rolf Pütter, Horst Behre. ‌
↑ Patent EP0002691 : Process for the preparation of 1-aminonaphthalene-3,6,8-trisulfonic acid. Registered on December 6, 1978 , published on July 11, 1979 , applicant: Bayer AG, inventor: Rudolf Braden, Horst Behre, Heinz Ziemann. ‌

[GESTIS-1] Entry on sodium hydrogen 4-amino-5-hydroxynaphthalene-2,7-disulfonate in the GESTIS substance database of the IFA , accessed on October 9, 2018(JavaScript required) .

[2] External identifiers of or database links for sodium 4-amino-5-hydroxy-7-sulfo-2-naphthalene sulfonate : CAS number: 5460-09-3, EC number: 226-736-4, ECHA - InfoCard: 100.024.306 , GESTIS substance database : 494656 , PubChem : 23664361 , ChemSpider : 20310 , Wikidata : Q72439883 .

[Bay1-3] Patent DE2732266 : Process for the production of 1-amino-8-naphthol-3,6-disulfonic acid (H-acid). Registered on July 16, 1977 , published on February 1, 1979 , applicant: Bayer AG, inventor: Willi Schößler, Rolf Pütter, Horst Behre. ‌

[Bay2-4] Patent EP0002691 : Process for the preparation of 1-aminonaphthalene-3,6,8-trisulfonic acid. Registered on December 6, 1978 , published on July 11, 1979 , applicant: Bayer AG, inventor: Rudolf Braden, Horst Behre, Heinz Ziemann. ‌