Process for the preparation of 1,5-dihydroxynaphthalene and 1,5-diaminonaphthalene

US4973758A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Horst Behre · Odenthal, DE
• Lothar Jakob · Wolfratshausen, DE
• Heinz U. Blank · Odenthal, DE
• Dietmar Mayer · Bensberg, DE
• Roland Busse · Cloppenburg, DE

Key dates

• Filing date: Nov 21, 1989
• Grant date: Nov 27, 1990
• Expiry date: Nov 21, 2009

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C211/58
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

The characteristic of the improved process for the preparation of 1,5-dihydroxynaphthalene and 1,5-diaminonaphthalene is to carry out the alkaline pressure hydrolysis of the disodium salt of naphthalene-1,5-disulphonic acid at temperatures from 270.degree. to 290.degree. C. and under 14 to 20 bar using an excess of sodium hydroxide solution such that the molar ratio NaOH/disodium salt of naphthalenesulphonic acid is at least 12:1. The 1,5-dihydroxynaphthalene which is obtained in this manner, without hazard and in substantially higher purity, is then aminated with ammonia in the presence of ammonium bisulphite to give 1,5-diaminonaphthalene, it being possible to achieve a further increase in the degree of purity of the 1,5-diaminonaphthalene by increasing the molar ratio NH.sub.3 /1,5-dihydroxynaphthalene to at least 6:1.