Process for the continuous preparation of 3,3'-dichloro-benzidine dihydrochloride

US5208376A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Kurt Habig · Mörfelden, DE
• Konrad Baessler · Frankfurt am Main, DE
• Klaus Warning · Eppstein, DE

Key dates

• Filing date: Jun 8, 1992
• Grant date: May 4, 1993
• Expiry date: Jun 8, 2012

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C209/54
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

A process for the continuous preparation of 3,3'-dichlorobenzidine dihydrochloride from 2,2'-dichlorohydrazobenzene by treatment with aqueous sulfuric acid, which comprises treating the 2,2'-dichlorohydrazobenzene, dissolved in a water-immiscible aromatic solvent, continuously at temperatures of from about 20.degree. to about 50.degree. C. in the presence of an alkali metal salt of an alkyl (C.sub.8 -C.sub.23)polyglycol ether sulfate, with such an amount of from about 50 to about 80 % strength aqueous sulfuric acid that the suspension formed remains conveyable, subsequently diluting the suspension emerging from the reaction zone with water, again continuously, and subsequently heating the suspension to a temperature of from about 90.degree. to about 95.degree. C. until a solution is obtained, separating off the aromatic solvent from the hot, sulfuric acid aqueous phase, and precipitating the 3,3'-dichlorobenzidine dihydrochloride by adding hydrochloric acid to the sulfuric acid solution which remains and filtering off this product.