CS196476B1 - Method of preparing halogenated aromatic primary amines - Google Patents

Description

The invention relates to a process for the preparation of halogenated aromatic primary amines by reduction of the corresponding Bochampa nitro compound in the presence of an effective dechloraee inhibitor.

It is generally known that the reduction of halogenated aromatic nitro compounds is accompanied by a loss of chlorine to form aromatic primary amines and less halogen than desired or dehalogenated at all. They then form impurities which accompany the main component of the crude product and must be removed predominantly by fractional distillation.

The halogen of the aromatic nucleus is tightly bound by the sioe and is usually cleaved only by high temperatures. However, a completely different situation is due to the presence of certain substituents which have a negative effect on the stability of the chlorine. Such are, for example, -NOg, -CN, -COOH in the ortho- or para-position to the back, which makes it mobile. The reactivity of chlorine is mainly increased by the -NOg group.

It has therefore been expedient to focus ee on suppressing the dehalogenation that accompanies the main process of the Baohamp reduction of aromatic halogen nitro compounds, with an effective inhibitor of this reaction.

Of course, many substances are known to be dehlorination inhibitors. Their inhibitory

196 476

However, the IBS 47β effect is not particularly significant, or significantly reduces the reaction rate of the reduction, extending the working time of the manufacturing operation and is therefore not of interest or unacceptable for corrosive reasons. Thus, FP No. 1534361 discloses the use of triethylfoephite, USP No. 3149161 the use of sodium acetate, Japanese patent application SHO 50-31134 discloses the use of calcium compounds and, in addition, other substances from the group of alkylamines, alconoamines, ala.cyclic amines and the like.

It was necessary to find an inhibitor which, under the operating conditions of the Béchamp reduction, in particular the reduction of 2,5-diohloronitrobenzene and ortho-chloro-nitrobenzene, significantly suppressed the formation of by-products originating from the dehalogenation reaction.

It has been found that such a substance may be, for example, dlcyanediamide, calcium cyanamide, either pure or in the form of a fertilizer, and cyanamide, which have the additional advantage that they do not adversely affect or affect the reaction rate of reduction.

Of these three compounds, particularly preferred is dlkyanediamide, which was used in laboratory experiments of Béchamp reduction of recrystallized 2,5-dichloronitrobenzene to give a product of 99.7% purity, containing only 0.15% by weight. % Of 3-chloroaniline and 0.15 wt. 2-chloroaniline, whereas an experiment without using this inhibitor yielded the product of only 97.2% purity. The process for the preparation of halogenated aromatic primary amines of the formula I,

wherein X is H or Cl, by Bechampt reduction of the corresponding nitroelements of formula II,

Cl

(11) wherein X is as defined above, in the presence of dechloraee inhibitors, according to the invention, is added as a dechloraee inhibitor to the system from 0.1 to 30 wt.

The commercial scale application of dicyandiamide in the production of 2,5-diohloraniline had the same positive effect of the inhibitor, which resulted in a significant reduction in the mono-chloroaniline and aniline content in the system after reduction, compared to production batches where the inhibitor was not used.

Example 1

A Béehamp reduction of 2,5-dichloronitrobenzene was carried out in a system containing a bowl of 478 g of water, 120 g of Fe-pilin and 0.816 g of formic acid to which 120 g of 2,5-dichloronitrobenzene was introduced. Prior to the reduction, 6.0 g of dlkyandl amide was introduced into the reduction system. The reduction was carried out at boiling point for three hours to give a product containing 99.7% by weight. % Of 2,5-dichloroaniline, 0.15 wt. % Of 2-chloroaniline and 0.15 wt. 3-chloroaniline.

Under the same conditions, an experiment without the Inhibitor provided a product of content

97.2% wt. % Of 2,5-dichloroaniline, 1.0 wt. % Of 2-chloroaniline, 1.4 wt. % Of 3-chleraniline and 0.4 wt. aniline.

Example 2

The Béohamp reduction was carried out in a system containing 900 kg of water, 1500 kg of Pepinin, 12.5 kg of formic acid, 15 kg of dicyandiamide and 1500 kg of technical 2,5-diohloronitrobenzene for 14 hours at boiling point. The crude product contained:

99.2% 2,5-dichloroaniline 0.3% 2-chloroaniline 0.2% 3-chloroaniline 0.1% 2,4-dichloroaniline 0.2% 3,4-dichloroaniline%% by weight *

The composition of the product without the use of Inhibitor was as follows:

95.0% 2,5-dichloroaniline 1.7% 2-chloroaniline 2.1% 3-chloroaniline 0.1% 2,4-dichloroaniline 0.2% 3,4-dichloroaniline 0.1% aniline

Said% is% by weight.

Example 3

The Béohamp reduction was carried out in a system containing 60 g of water, 60 g of Pepinin, 7.9 g of HCl and 120 g of ortho-carbonornobenzene e by adding 3.6 g of cyanamide. . % ortho-chloroaniline, 0.2 wt. % para-chloroaniline and 0.1 wt. aniline. The comparative experiment without inhibitor showed only 98.6% by weight. % ortho-chloroaniline and 0.2 wt. para-chloroaniline and above all

1.2% aniline.

Example 4

Béohamp reduction of 2,5-dichloronitrobenzene was carried out in a system containing

72.5 g of water, 120 g of Piperine and 0.99 g of kya. formic, in which 120 g of 2,5-di1 · (471 ohlornitrobenzene) was introduced. 6.0 g of calcium cyanamide in the form of a teohnic fertilizer were used as the deohloroase inhibitor.

The reduction was carried out at the boiling point of the system for 6 hours to give a product containing 99.1% by weight. 2,5-dichloroaniline, 0.4 wt.% 2-chloroaniline and 0.5 wt. 3-Coolediline.

Bac use of the inhibitor was the content of deohloraoe products at the level of previous experiments.

Claims (1)

SUBJECT OF THE INVENTION A process for the preparation of halogenated aromatic primary amines of Formula I wherein X is H or Cl by Behehamp reduction of the corresponding nitro compounds of Formula II, (II) wherein X is as hereinbefore defined in the presence of deohloroase inhibitors. 0.1 to 30 wt. based on the weight of the nitroalloy compound, cyanamide, calcium cyanamide or dicyandiamide. Printed by Moravian Printing Works,