7-hydroxynaphthalene-1-sulphonic acid
- CAS NO.：132-57-0
- Empirical Formula: C10H8O4S
- Molecular Weight: 224.23
- EINECS: 205-066-6
- SAFETY DATA SHEET (SDS)
- Update Date: 2026-05-12 09:17:10
What is 7-hydroxynaphthalene-1-sulphonic acid?
Chemical properties
Colorless crystals. Easily soluble in water and alcohol. 2-Hydroxynaphthalene-8-sulfonic acid [132-57-0]. (7-hydroxynaphthalene-1-sulfonic acid), crocein acid, Bayer’s acid, C10H8O4S, Mr 224.23, is more soluble in water than 2-hydroxynaphthalene-6-sulfonic acid and cannot readily be isolated. Its salts are also more soluble than their 2,6-analogues and are difficult to isolate. On evaporation of its solutions, the free acid (2-Hydroxynaphthalene-8-sulfonic acid) decomposes to 2-naphthol. Coupling with diazo compounds takes place in the 1-position, but reaction is hindered by the peri-sulfonic acid group so that concentrated conditions and sometimes catalysts are required. Above 60 ℃, sulfuric acid converts 2-Hydroxynaphthalene-8-sulfonic acid into 2-hydroxynaphthalene-6-sulfonic acid; sulfonation then proceeds further to give the 6,8-disulfonic acid. Amination (Bucherer reaction) gives 2-aminonaphthalene8-sulfonic acid.
The Uses of 7-hydroxynaphthalene-1-sulphonic acid
Used as an intermediate of acid dyes and direct azo dyes.
Preparation
7-hydroxynaphthalene-1-sulphonic acid was prepared by sulfonation of 2-naphthol with 98% sulfuric acid at low temperature.
Properties of 7-hydroxynaphthalene-1-sulphonic acid
| Boiling point: | 335.63°C (rough estimate) |
| Density | 1.4643 (rough estimate) |
| refractive index | 1.5400 (estimate) |
| pka | 0.26±0.40(Predicted) |
| EPA Substance Registry System | 1-Naphthalenesulfonic acid, 7-hydroxy- (132-57-0) |
Safety information for 7-hydroxynaphthalene-1-sulphonic acid
Computed Descriptors for 7-hydroxynaphthalene-1-sulphonic acid
New Products
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![disodium 8-[[3,3'-dimethoxy-4'-[[4-[[(p-tolyl)sulphonyl]oxy]phenyl]azo][1,1'-biphenyl]-4-yl]azo]-7-hydroxynaphthalene-1,3-disulphonate](https://img.chemicalbook.in/CAS/GIF/6548-30-7.gif)
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