Tobias Acid

Description

Tobias Acid · CAS 81-16-3 · C10H9NO3S. UNII F9QKW1FCE0. Solubility: In water, 4,100 mg/l @ 20 °C; LogP: log Kow= -1.16; LogP: -1.16.

Identification

CAS Registry Number	81-16-3
PubChem CID	6670
Molecular formula	C10H9NO3S
IUPAC name	2-aminonaphthalene-1-sulfonic acid
UNII (FDA)	F9QKW1FCE0

Computed Descriptors

Molecular Weight	223.25
XLogP3	1.8
Hydrogen Bond Donor Count	2
Hydrogen Bond Acceptor Count	4
Rotatable Bond Count	1
Exact Mass	223.03031432
Monoisotopic Mass	223.03031432
Topological Polar Surface Area	88.8
Heavy Atom Count	15
Formal Charge	0

Physical & Chemical Properties

Solubility	In water, 4,100 mg/l @ 20 °C
LogP	log Kow= -1.16
LogP	-1.16
Dissociation Constants	pK1= 2.35 in water @ 25 °C

Physical description & handling notes

• White solid; [HSDB] Light orange crystalline powder; [MSDSonline]
• WHITE NEEDLES
• Anhydrous scales from hot water; hydrated needles from cold water
• Slightly sol in cold water; more sol in hot water; very slightly sol in alcohol, ether
• When heated to decomp it emits very toxic fumes of /nitrogen oxides and sulfur oxides/.

Regulatory Status

GHS notification summary	76.5% (26 / 34)

GHS Hazard Classification

GHS notification summary	76.5% (26 / 34)
Reported hazard statements	H319 (20.6%)

Documented Uses

• Used in optical brighteners and as a diazo component in acid dyes , red reactive dyes, and pigments; [HSDB]
• Tobias acid is used as a diazo component in acid dyes (eg, C.I. Acid Yellow 19), red reactive dyes, and pigments such as the important Lithol Reds, (eg, C.I. Pigment Red 49).
• Azo dye intermediate, optical brighteners
• PREPD BY SULFONATION OF 2-NAPHTHYLAMINE: TINKER, HANSEN, US PATENT 1,969,189 (1934 TO DU PONT).
• Sulfonation of beta-naphthol with chlorosulfonic acid in nitrobenzene at 0 °C followed by heating the resulting 1-sulfonic acid with ammonium hydrogen sulfite and ammonia at 145-150 °C. Purification is by precipitation from dilute solution of the sodium salt.
• By amination of the appropriate hydroxynaphthalenesulfonic acid.

Synonyms

81-16-3; 2-AMINO-1-NAPHTHALENESULFONIC ACID; Tobias acid; 2-Naphthylamine-1-sulfonic acid; Kyselina tobiasova; 1-Naphthalenesulfonic acid, 2-amino-; F9QKW1FCE0; Kyselina 2-naftylamin-1-sulfonova; DTXSID7020922; NSC-5523; DTXCID90922; RefChem:463279; 201-331-5; 2-aminonaphthalene-1-sulfonic acid; CCRIS 9048; MFCD00003988

Frequently Asked Questions

What are the CAS number and molecular formula of Tobias Acid?

CAS 81-16-3; molecular formula C10H9NO3S; molecular weight — g/mol.

What other names is Tobias Acid known by?

81-16-3, 2-AMINO-1-NAPHTHALENESULFONIC ACID, Tobias acid, 2-Naphthylamine-1-sulfonic acid, Kyselina tobiasova, 1-Naphthalenesulfonic acid, 2-amino-.

Is Tobias Acid classified as hazardous?

76.5% of GHS notifications report no hazard classification (26 of 34).

What are the key physical properties of Tobias Acid?

Solubility: In water, 4,100 mg/l @ 20 °C; LogP: log Kow= -1.16; LogP: -1.16; Dissociation Constants: pK1= 2.35 in water @ 25 °C.

Facts on this page are taken from PubChem (US National Library of Medicine) and Wikidata. Grade-specific data — assay, moisture, particle size, packaging, shelf life — is issued per batch on the COA and is not published here.