Hydroxynaphthalenesulfonic acid refers to organic compounds with the formula C10H6(SO3H)(OH). Several are precursors to azo dyes and to various aminonaphthalenesulfonic acids. [1] They are colorless solids with high solubility in water.
| name | Registry number | m.p., °C | prep | Precursor to |
|---|---|---|---|---|
| 1-Hydroxynaphthalene-2-sulfonic acid "Baum’s acid" | 567-18-0 | 250 | by low T sulfonation of 1-naphthol together with 4-hydroxynaphthalene-2-sulfonic acid | |
| 1-Hydroxynaphthalene-3-sulfonic acid | 3771-14-0 | ? | acid hydrolysis of 1-aminonaphthalene-3-sulfonc acid | |
| 1-Hydroxynaphthalene-4-sulfonic acid "Nevile and Winther’s acid", "N&W acid" | 84-87-7 | 170 | by low T sulfonation of 1-naphthol together with 4-hydroxynaphthalene-2-sulfonic acid | C.I. Acid Orange 19, C.I. Mordant Brown 35, C.I. Food Red 3 |
| 1-Hydroxynaphthalene-5-sulfonic acid "oxyL acid", "Azurin acid" | 117-59-9 | ? | base hydrolysis of 1,5-naphthalenedisulfonic acid | C.I. Pigment Red 54, C.I. Mordant Black 29 |
| 1-Hydroxynaphthalene-5-sulfonic acid | 16500-22-4 | ? | obscure | |
| 1-Hydroxynaphthalene-7-sulfonic acid | 20191-62-2 | ? | obscure | desulfonation of 1-hydroxy-2,7- and 1-hydroxy-4,7-disulfonic acids |
| 1-Hydroxynaphthalene-8-sulfonic acid | 117-22-6 | 106 (monohydrate) | ? | C.I. Acid Black 54, C.I. Acid Blue 158 |
| 2-Hydroxynaphthalene-1-sulfonic acid "oxy Tobias acid", "Stebbins acid" | 567-47-5 | 115 | low T sulfonation of 2-naphthol | 2-aminonaphthalene-1-sulfonic acid (Tobias acid) |
| 2-Hydroxynaphthalene-3-sulfonic acid | 16435-40-8 | ? | obscure | |
| 2-Hydroxynaphthalene-4-sulfonic acid | 6357-85-3 | ? | by desulfonation of 2-hydroxynaphthalene-4,8-di-sulfonic acid | |
| 2-Hydroxynaphthalene-5-sulfonic acid | 20386-27-0 | ? | obscure | |
| 2-Hydroxynaphthalene-6-sulfonic acid | 93-01-6 | 129 (monohydrate) | sulfonation of 2-naphthol | C.I. Acid Orange 12, C.I. Food Yellow 3, C.I. Food Orange 2 |
| 2-Hydroxynaphthalene-7-sulfonic acid "Cassella's acid" | RN [92-40-0 | 89 (monohydrate) | ? | 2-aminonaphthalene-7-sulfonic acid ,2-hydroxynaphthalene-3,7-disulfonic acid, |
| 2-Hydroxynaphthalene-8-sulfonic acid croceic acid | 132-57-0 | ? | C.I. Acid Red 25 | |
In addition to these compounds, several dihydroxynaphthalenes, naphthalenedisulfonic acids, naphthalenetrisulfonic acids, hydroxynaphthalenedisulfonic acids, hydroxynaphthalenetrisulfonic acids, and aminonaphthalenesulfonic acids are valuable.