Single-vessel process for preparing 2-acetaminonaphthalene-6-sulfonic acid of high purity
AssigneeHoechst Aktiengesellschaft
InventorsOtto Arndt, Theodor Papenfuhs
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Abstract
A single-vessel process for preparing 2-acetaminonaphthalene-6-sulfonic acid of high purity by sulfonating 2-hydroxynaphthalene with concentrated sulfuric acid, converting the 2-hydroxynaphthalenesulfonic acid formed with ammonia in the presence of ammonium hydrogensulfite into 2-amino-naphthalene-6-sulfonic acid (Bucherer reaction) and N-acetylating the latter to give 2-acetaminonaphthalene-6-sulfonic acid, which comprises, after diluting the sulfonating melt with water, substantially removing any impurities still present in the resulting aqueous solution of 2-hydroxynaphthalene-6-sulfonic acid, in particular 2-hydroxynaphthalene, by extraction with toluene or xylene and/or clarification using active carbon.
Claims3
In a single-vessel process for preparing 2-acetaminonaphthalene-6-sulfonic acid of high purity by sulfonating 2-hydroxynaphthalene with concentrated sulfonic acid, converting the 2-hydroxynaphthalenesulfonic acid formed thereby with ammonia in the presence of ammonium hydrogensulfite into 2-aminonaphthalene-6-sulfonic acid (Bucherer reaction) and N-acetylating the said 2-aminonaphthalene-6-sulfonic acid to give 2-acetaminonaphthalene-6-sulfonic acid, the improvement which comprises:
- after diluting the sulfonating melt with water, substantially removing any impurities still present in the resulting aqueous solution of 2-hydroxynaphthalene-6-sulfonic acid by clarification using active carbon.
In a single-vessel process for preparing 2-acetaminophthalene-6-sulfonic acid of high purity by sulfonating 2-hydroxynaphthalene with concentrated sulfuric acid, converting the 2-hydroxynaphthalenesulfonic acid formed thereby with ammonia in the presence of ammonium hydrogensulfite into 2-aminonaphthalene-6-sulfonic acid (Bucherer reaction and N-acetylating the said 2-aminonaphthalene-6-sulfonic acid to give 2 acetaminonaphthalene-6-sulfonic acid, the improvement which comprises:
- after diluting the sulfonating melt with water, substantially removing any impurities still present in the resulting aqueous solution of 2-hydroxynaphthalene-6-sulfonic acid by extraction with toluene or xylene and clarification using active carbon.
Dependencies are inferred from the claim text.