Single-vessel process for preparing 2-acetaminonaphthalene-6-sulfonic acid of high purity

US4908478A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Otto Arndt · Hofheim, DE
• Theodor Papenfuhs · Frankfurt, DE

Key dates

• Filing date: Nov 10, 1988
• Grant date: Mar 13, 1990
• Expiry date: Nov 10, 2008

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C309/51
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

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.