Naphthalenedisulfonic acid
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Naphthalenedisulfonic acid refers to organic compounds with the formula C10H6(SO3H)2. They are derivatives of naphthalene. Twelve isomers are possible, but only a few have been examined in some depth, often as precursors to azo dyes or to various drugs.[1] They are colorless solids with high solubility in water. Some derivatives are prepared by sulfonation of naphthalene or its monosulfonic acids. A few are produced by indirect routes.
| name | Registry number | m.p., °C | prep | Precursor to | |
|---|---|---|---|---|---|
| 1,3-Naphthalenedisulfonic acid | 6094-26-4 | 250 | deamination 2-aminonaphthalene-6,8-disulfonic acid | obscure | |
| 1,5-Naphthalenedisulfonic acid, Armstrong acid | 81-04-9 | 240-245 | sulfonation of naphthalene with oleum (together with 1,6-isomer) | 1-hydroxynaphthalene-5-sulfonic acid, 1,5-dihydroxynaphthalene, 1,3,5-naphthalenetrisulfonic acid | |
| 1,6-Naphthalenedisulfonic acid | 525-37-1 | 125 | sulfonation of naphthalene with oleum (together with 1,5-isomer) | 1,6-dihydroxynaphthalene, 1,3,6-naphthalenetrisulfonic acid | |
| 1,7-Naphthalenedisulfonic acid | 5724-16-3 | ? | low T sulfonation of naphthalene-2-sulfonic acid in low yields | obscure | |
| 2,6-Naphthalenedisulfonic acid | 581-75-9 | ? | high T sulfonation of naphthalene | 2-hydroxynaphthalene-6-sulfonic acid and 2,6-dihydroxynaphthalene | |
| 2,7-Naphthalenedisulfonic acid | 92-41-12 | ? | high T sulfonation of naphthalene | 2-hydroxynaphthalene-7-sulfonic acid, 2,7-dihydroxynaphthalene | - |
| 1-Aminonaphthalene-8-hydroxy-2,4-disulfonic acid (Chicago acid) | 82-47-3 | ? | base hydrolysis of naphthosultam-2,4-disulfonic acid | precursor to C.I. Direct Blue 1 199, Direct Blue 22, Direct Blue 76[2] |
In addition to these compounds, several naphthalenetrisulfonic acids are known as well as several hydroxy derivatives.