2-Aminonaphthalene-1-sulfonic acid Chemical 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)

NIST Chemistry Reference

2-Naphthylamine-1-sulfonic acid(81-16-3)

EPA Substance Registry System

2-Amino-1-naphthalenesulfonic acid (81-16-3)

Safety Information

Risk Statements 

36/37/38-40

Safety Statements 

26-36/37/39

RIDADR 

2585

WGK Germany 

1

RTECS 

QK1250000

TSCA 

Yes

HS Code 

2921.45.9010

HazardClass 

8

PackingGroup 

III

Hazardous Substances Data

81-16-3(Hazardous Substances Data)

MSDS

• Language:English Provider:2-Naphthylamine-1-sulfonic acid
• Language:English Provider:SigmaAldrich
• Language:English Provider:ALFA

2-Aminonaphthalene-1-sulfonic acid Usage And Synthesis

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.

Uses

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.

Uses

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.]

2-Aminonaphthalene-1-sulfonic acid(81-16-3)Related Product Information

• 1-Naphthylamine
• Taurine
• Amlodipine Besylate
• Ethyl 2-(Chlorosulfonyl)acetate
• p-Toluenesulfonic acid
• Sulfanilic acid
• Ammonium sulfamate
• Sulfamic acid
• Molasses
• 4-Amino-benzenesulfonic acid monosodium salt
• 1-DODECANESULFONIC ACID SODIUM SALT
• 1,5-Naphthalenedisulfonic acid
• 2-Naphthylamine
• Glycine
• Folic acid
• 1-Naphthalenesulfonic acid
• Sulfamic acid monosodium salt
• Nickel bis(sulphamidate)