Naphthalene-2,7-disulfonic acid Property

Melting point:

199°C

Boiling point:

400.53°C (rough estimate)

Density 

1.6867 (rough estimate)

refractive index 

1.6950 (estimate)

storage temp. 

2-8°C

pka

-0.33±0.40(Predicted)

CAS DataBase Reference

92-41-1(CAS DataBase Reference)

EPA Substance Registry System

2,7-Naphthalenedisulfonic acid (92-41-1)

Safety

RIDADR 

1759

HazardClass 

8

PackingGroup 

III

HS Code 

2904100090

Hazard and Precautionary Statements (GHS)

Symbol(GHS)

Signal word

Danger

Hazard statements

H314Causes severe skin burns and eye damage

Precautionary statements

P260Do not breathe dust/fume/gas/mist/vapours/spray.

P280Wear protective gloves/protective clothing/eye protection/face protection.

P310Immediately call a POISON CENTER or doctor/physician.

Naphthalene-2,7-disulfonic acid Chemical Properties,Usage,Production

Chemical Properties

White, crystalline solid.Soluble in water. Combustible. Naphthalene-2,7-disulfonic acid [92- 41-1]. C10H8O6S2, Mr 288.28; the sodium salt of Naphthalene-2,7-disulfonic acid is much more soluble than that of the 2,6- isomer but can be isolated and purified by precipitation of the calcium salt at lower temperature followed by recrystallization.

Uses

Intermediate for dyes. The disodium salt of 8 gives 2-hydroxynaphthalene-7-sulfonic acid or 2,7-dihydroxynaphthalene by fusion processes. Sulfonation by oleum gives the 1,3,6-trisulfonic acid, and nitration gives 1-nitronaphthalene-3,6- disulfonic acid. In sulfuric acid solution, the disodium salt of naphthalene-2,7-disulfonic acid undergoes an unusual reaction at the 4-position with 4,40 -bis- (dimethylamino)benzhydrol. The resulting condensation product is oxidized with lead dioxide to give the acid basic dye C.I. Acid Green 16.

Production Methods

The 2,7-disulfonic acid is always the main product of high-temperature sulfonation of naphthalene, but at 160 C it converts slowly to an equilibrium mixture containing ca. 30 % of the 2,6-isomer. Crystallization of the pure product from conventional sulfonation is difficult, and alternative processes, (for example, reaction of naphthalene vapor with sulfur trioxide in the gas phase at 220 C) are said to give a purer product.

Definition

ChEBI: A naphthalenesulfonic acid in which the sulfo groups are attached to positions 2 and 7 of the naphthalene ring.

Purification Methods

Crystallise the acid from conc HCl. The disulfonamide has m 273o (from EtOH). [Beilstein 11 II 119, 11 III 463.]