CS202957B1 - Method of producing 2-nitro-1,3,5-trimethyl-benzene - Google Patents

Description

(54) Production method of 2-nitro-1,3,5-trimethylbenzene /

The invention relates to a process for the preparation of 2-nitro-1,3,5-trimethylbenzene by treating nitric acid with 1,3,5-trimethylbenzene in acetic anhydride.

2-Nitro-1,3,5-trimethylbenzene (nitromesitylene) is an intermediate for the production of 2-amino-1,3,5-trimethylbenzene (mesidine), which is an important dye and pharmaceutical raw material.

At. hitherto known processes for the production of nitromesitylene by nitration of 1,3,5-trimethylbenzene (mesitylene) were, for example, sulfuric acid, acetonitrile, acetic anhydride, acetic acid or mixtures thereof, and inorganic salts of nitric acid, benzoyl nitrate, nitric acid mixtures were used as nitrating agents. with sulfuric acid, or with acetic hydride and acetic acid, and optionally acetonitrile and sulfuric acid. All known production processes are complicated by intensive cooling to allowable temperatures in the range of 0 to 20 ° C, usually up to 15 ° C, both in the preparation of the nitration mixtures and in the mixing of the nitrating acid with the nitrated substance.

In addition, nitration in sulfuric acid environments required vigorous stirring and additions of adjuvants to improve the reaction or to reduce the formation of resinous impurities, such as the addition of urea, amidosulfonic acid, polyethylene glycol isooctylphenol or. methylethylaikoxymethylammonium methylsulphate.

These disadvantages are overcome by a process for the preparation of 2-nitro-1,3,5-trimethylbenzene from 1,3,5-trimethylbenzene in acetic anhydride by the action of nitric acid, which is based on the fact that it is introduced into the reaction mixture at 25 to 100 ° C. % nitric acid having a concentration of 60 to 80%, preferably 65 to 69.2% by weight;

Excess acetic anhydride and acetic anhydride reaction product with nitric acid is possible after finished nitration hydrolyzed by adding 1 to 5 times the stoichiometric amount of water and product isolation make vacuum distillation at temperatures up to 100 C. ^At a pressure of 10 kPa. In this way, concentrated acetic acid is obtained in addition to the main product. Isolation of the product can also be carried out in a conventional manner by diluting the reaction mixture with water and separating the aqueous phase from the nitromethene phase. The nitrous acid can be nitrated directly with the process according to the invention, and the preparation of a nitration mixture, which is always associated with the release of a considerable amount of heat and thus a danger, is eliminated.

Carrying out the reaction at a temperature higher than usual makes it possible to use instead of brine to cool the water and to accelerate the dosing of nitric acid into the reaction mixture, since the nitric acid and its intermediate 8 with acetic anhydride are immediately consumed by the reaction and cannot accumulate in the reaction mixture. 3,5-trinxethylbenzene. The product is predominantly a mononitroderivative, obtained as a yellow crystalline solid having a melting point above 36 ° C, containing only a small amount of eutectic at room temperature. The yield of the isolated product exceeds 80% of the theory based on 1,3,5-trimethlybenzene * Product quality is better in appearance and impurity content than the quality of the product obtained by nitration of 1,3,5-trimethylbenzene in sulfuric acid, purified by repeated washing with diluted lye and water. The quality of the product obtained according to the invention makes it possible to process it without purification directly by reducing the lower phase after diluting the reaction mixture with water and separating the aqueous layer.

In the case of a possible washing of the crude product with water, the second wash adds sodium or potassium hydroxide solution to achieve a pH of washing water in the range of 7.5 to 8. Neutral reaction is readily achieved since the crude product does not contain resins or other by-products to promote stable emulsions . The product thus purified can be stored without the risk of corrosive action. The unpurified product, after isolation by vacuum distillation or after isolation from a reaction mixture diluted with water, is suitable for direct processing to 2-aminoTi, 3,5-triraethylbenzene / mesidine / iron reduction by Bechamp.

In order to illustrate the invention, the following examples are given.

Example 1

To a mixture of 120.2 g of 1,3,5-trimethylbenzene and 300 g of acetic anhydride, a total of 101 g of 65.5% by weight nitric acid was gradually added over 2 hours at a reaction temperature of 55-60 ° C. The reaction mixture was stirred for 15 minutes at 50-60 ° C and then undiluted with 750 g of water at 45 ° C. After separation of the diluted nitric acid / acetic acid upper layer, the crude nitromesitylene was washed at 45 ° C successively once with water, once with water with addition of sodium hydroxide solution to pH = 8 and then twice with water until removal of alkalinity. Nitro-1,3,5-trimethylbenzene *

Example 2

According to the procedure of Example 1, the reaction was carried out at a temperature of 30 to 35 ° C. Vacuum distillation at a pressure of 10 kPa eliminated volatiles in the reaction mixture gradually increased from 40 to 80 ° C. The distillation residue was purified by washing as well as the crude product in Example 1.

145 g of 2-nitro-1,3,5-trimethylbenzene were obtained.

Example 1 a d 3

The reaction and isolation of the product was carried out according to the procedure of Example 1. The crude product was subjected to Bechamp reduction. The yield of 2-amino-1,3,5-trimethylbenzene was 74 Z, calculated on the starting mesitylene.

He attaches

A mixture of 120.2 g of 1,3,5-trimethylbenzene and 310 g of acetic anhydride was nitrated according to Example 1. Then 9 g of water was added and the isolation according to Example 2 was obtained. 146 g of 2-nitro-1,3,5 were obtained. -trimethylbenzene.

Claims (2)

OF THE INVENTION Process for the preparation of 2-nitro-1,3,5-trimethylbenzene from 1,3,5-trimethylbenzene in acetic anhydride by the action of nitric acid, characterized in that it is introduced into the reaction mixture at a temperature of 25 to 100 ° C introduces nitric acid at a concentration of 60 to 80 Z, preferably 65 to 69.2 Z by weight. 2. The method of claim 1, wherein, to isolate the product, the excess acetic anhydride and its intermediate with nitric acid are hydrolysed after addition of nitration by adding 1 to 5 times to the stoichiometric amount of water and the volatiles are removed by vacuum distillation at temperatures up to 100 ° C. pressure up to 10 kPa.