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2-Aminonaphthalene-1-sulfonic acid

Chemical Name:
2-Aminonaphthalene-1-sulfonic acid
Nsc5523;TOBIAS ACI;TOBIAS ACID;TOBIAC ACID;SUPER J ACID;Tobiasacid,98%;Wln: L66J bswq cz;kyselinatobiasova;TOBIAS ACID 97 PCT;Kyselina tobiasova
Molecular Formula:
Molecular Weight:
MDL Number:
MOL File:
MSDS File:
Last updated:2023-11-03 13:07:37

2-Aminonaphthalene-1-sulfonic acid Properties

Melting point 180 °C
Boiling point 220°C (rough estimate)
Density 1.3588 (rough estimate)
refractive index 1.5250 (estimate)
storage temp. -20°C Freezer, Under inert atmosphere
solubility DMSO (Slightly), Methanol (Slightly, Heated), Water (Slightly, Heated)
form Solid
pka pK1: 2.35 (25°C)
color White to Off-White
Water Solubility 4.083g/L(20 ºC)
Merck 14,6406
BRN 613084
CAS DataBase Reference 81-16-3(CAS DataBase Reference)
EWG's Food Scores 1
NIST Chemistry Reference 2-Naphthylamine-1-sulfonic acid(81-16-3)
EPA Substance Registry System 2-Amino-1-naphthalenesulfonic acid (81-16-3)


Risk and Safety Statements

Symbol(GHS)  GHS hazard pictograms
Signal word  Warning
Hazard statements  H320-H319
Precautionary statements  P264-P305+P351+P338+P337+P313-P280i-P305+P351+P338-P337+P313
Risk Statements  36/37/38-40
Safety Statements  26-36/37/39
RIDADR  2585
WGK Germany  1
RTECS  QK1250000
HS Code  2921.45.9010
HazardClass  8
PackingGroup  III
NFPA 704
2 0

2-Aminonaphthalene-1-sulfonic acid price More Price(12)

Manufacturer Product number Product description CAS number Packaging Price Updated Buy
TCI Chemical A0343 2-Amino-1-naphthalenesulfonic Acid >98.0%(HPLC)(T) 81-16-3 25g $48 2023-06-20 Buy
TCI Chemical A0343 2-Amino-1-naphthalenesulfonic Acid >98.0%(HPLC)(T) 81-16-3 500g $408 2023-06-20 Buy
Alfa Aesar A18644 2-Aminonaphthalene-1-sulfonic acid, 98% 81-16-3 500g $67.2 2023-06-20 Buy
Alfa Aesar A18644 2-Aminonaphthalene-1-sulfonic acid, 98% 81-16-3 2500g $239 2023-06-20 Buy
TRC A618330 2-Amino-1-naphthalenesulfonic Acid 81-16-3 250g $120 2021-12-16 Buy
Product number Packaging Price Buy
A0343 25g $48 Buy
A0343 500g $408 Buy
A18644 500g $67.2 Buy
A18644 2500g $239 Buy
A618330 250g $120 Buy

2-Aminonaphthalene-1-sulfonic acid Chemical Properties,Uses,Production

Chemical Properties

Grey white to light pink powder. 2-Aminonaphthalene-1-sulfonic acid [81-16-3].  Tobias acid, C10H9NO3S, Mr 223.24, is sparingly soluble in water but the sodium salt is readily soluble. Coupling with diazo compounds takes place in the 1-position with elimination of the sulfonic acid group.


Azo dye intermediate, optical brighteners. Sulfonation with oleum gives 2-aminonaphthalene-1,5-disulfonic acid, which can be desulfonated to produce 2-aminonaphthalene-5- sulfonic acid. Tobias acid is used as a diazo component in acid dyes (e.g., C.I. Acid Yellow 19), red reactive dyes, and pigments such as the important Lithol Reds, [e.g., C.I. Pigment Red 49]. The free acid of C.I. Pigment Red 49 is also remarkably insoluble and can be used as a pigment.


2-Amino-1-naphthalenesulfonic acid has been used in the preparation of 2-(2-naphthylamino)benzoxazole by reacting with 2-chlorobenzoxazole.

Production Methods

2-Hydroxynaphthalene-1-sulfonic acid is heated with a mixture of ammonia and ammonium sulfite in an autoclave at 150 ℃ and 1 MPa for 30 h. The reaction mixture is added to a slurry of lime, and excess ammonia is driven off. Inorganic calcium salts are filtered off at 80℃, and the filtrate is acidified with hydrochloric acid at 40℃ to precipitate Tobias acid in 95 % yield. Care must be taken throughout the process to avoid desulfonation and formation of 2- naphthylamine.

General Description

2-Amino-1-naphthalenesulfonic acid is a manufacturing intermediate in the monosulfo monoazo color additive D&C Red No. 34 and its lakes.

Purification Methods

Crystallise the acid under nitrogen from boiling water and dry it in a steam oven [Bryson Trans Faraday Soc 47 522, 527 1951]. [Beilstein 14 III 2240, 14 IV 2792.]

Synthesis of 2-Aminonaphthalene-1-sulfonic acid from Morpholine and 1-Amino-8-hydroxynaphthalene-3,6-disulphonic acid and 1,2,3-Triazine, 4,5,6-trifluoro-
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View Lastest Price from 2-Aminonaphthalene-1-sulfonic acid manufacturers

Image Update time Product Price Min. Order Purity Supply Ability Manufacturer
2-Aminonaphthalene-1-sulfonic acid pictures 2023-08-16 2-Aminonaphthalene-1-sulfonic acid
US $0.00 / KG 1KG 99% 50000KG/month Hebei Mojin Biotechnology Co., Ltd
2-Aminonaphthalene-1-sulfonic acid pictures 2023-03-29 2-Aminonaphthalene-1-sulfonic acid
US $5.00-2.00 / KG 1KG 99% 10000kg Hebei Crovell Biotech Co Ltd
2-Aminonaphthalene-1-sulfonic acid pictures 2023-03-18 2-Aminonaphthalene-1-sulfonic acid
US $6.00 / kg 1kg 99% 20 tons Hebei Duling International Trade Co. LTD
SUPER J ACID 2 NAPHTHYLAMINE SULPHONIC ACID 2-NAPHTHYLAMINE-1-SULFONIC ACID 2-AMINO-1-NAPHTHALENESULFONIC ACID 2-AMINONAPHTHALENE-1-SULFONIC ACID TOBIAS ACID 1-Naphthalenesulfonic acid, 2-amino- 1-Naphthalenesulfonicacid,2-amino- 2-amino-1-naphthalenesulfonic 2-amino-1-naphthalenesulfonicaci 2-aminonaphthalene-1-sulphonic acid TOBIAS ACID 97 PCT TOBIAS ACI TOBIAC ACID BETA-NAPHTHYLAMINE-1-SULFONIC ACID 2-amino-aphthalene-sulfonic acid Tobiasacid,98% 2-AMINO-1-NAPHTHALENESULPHONICACID 2-Naphthylamin-1-sulfonsure 2-NAPHTHYLAMINE-1-SULFONIC ACID (TOBIAS ACID) 2-Aminonaphthalin-1-sulfonsaure 1-Sulfo-2-naphthylamine Naphthalenesulfonic acid, 2-amino- Nsc5523 Wln: L66J bswq cz Tobias acid:2-Naphthylamine-1-sulfonic acid:Tobias acid 2-Amino-1-naphthalenesulfonic acid≥ 99% (Assay) Kyselina 2-naftylamin-1-sulfonova Kyselina tobiasova kyselina2-naftylamin-1-sulfonova kyselina2-naftylamin-1-sulfonova(czech) kyselinatobiasova kyselinatobiasova(czech) NaphthylaMine-1-sulfonic 2-amino-1-naphthalenesulfonate 2-Naphtylamine-1-Sulfonic Acid 2-Amino-1-naphthalenesulfonic Acid > 2-Naphthylamine-1-SulfonicAci 2-Aminonaphthalene-1-sulfonic acid ISO 9001:2015 REACH 81-16-3 C10H8NO3S Building Blocks Organic Building Blocks Sulfur Compounds Sulfonic/Sulfinic Acids Organics Intermediates Intermediates of Dyes and Pigments