CS210298B1 - Process for preparing 4-chloroaniline - Google Patents

Abstract

The invention describes the reduction of 4-chloronitrobenzene to 4-chloroaniline with zinc in the presence of calcium chloride in an aqueous-ethanolic medium. 4-Chloroaniline is used as an intermediate in the dyeing industry, and its described preparation is particularly suitable for producing less tonnage.

Description

The present invention relates to a process for preparing 4-chloroaniline by reducing 4-chloronitrobenzene with zinc and calcium chloride.

4-Chloroaniline (II) as one of the intermediates for the production of dyes and coloring agents is produced by reduction of 4-chloronitrobenzene (I) by the Béschamp reaction, ie reduction by iron in water

zinc in aqueous ethanolic calcium chloride solution. The reaction is carried out at 80 ° C and terminated by heating the reaction mixture to boiling. The product is isolated by pouring the reaction mixture on ice and suctioning off the precipitate. 4-Chloroaniline is obtained by this process in high yield and of satisfactory quality. The product obtained can generally be used for further synthesis without further purification.

The new process for the preparation of 4-chloroaniline is technologically undemanding and economically advantageous, especially for production of less tonnage.

(See, eg, Fierz-David and Blangley: Grundlegende Operationen der Farbenchemie, 5th Edition, 1947). After the reduction, the 4-chloroaniline was distilled off with water vapor from the reaction mixture. The resulting product is obtained in good yield and good quality, but the isolation time is very long. 4-Chloroaniline is a solid at normal temperature which clogs the distillation apparatus during distillation and presents considerable technological difficulties during distillation.

We have now found that by reducing 4-chloronitrobenzene (I) to 4-chloroaniline (II)

Example

To a solution prepared from 714 ml of absolute ethanol, 296 ml of water and 80 g of calcium chloride was added 64 g of zinc. The mixture was heated to 80 ° C and 177 g of 4-chloronitrobenzene was slowly added with stirring. After completion of the reaction, the mixture was heated to reflux for 2 hours. The reaction mixture was filtered and the insoluble residue in the flask or the filter was boiled with 320 ml of ethanol. The combined ethanolic filtrates were poured onto 500 g of ice. The precipitated 4-chloroaniline was aspirated and dried. 131 g (92% of theory) of b.p.

Claims (1)

A process for the preparation of 4-chloroaniline of formula II by reduction of 4-chloronitrobenzene of formula I ClCl is characterized in that the reduction is carried out with zinc in an aqueous-ethanolic calcium chloride solution at 80 ° C, the end product is isolated by pouring the reaction mixture into water and the precipitated product is filtered off with suction.