SU453392A1 - METHOD OF OBTAINING IODBENZEN - Google Patents

Description

one

The invention relates to a process for the preparation of iodobenzene, which is widely used in the preparation of ethyl benzene and Grignard reagents, and also as a solvent.

A known method of producing iodobenzene by iodizing benzene with iodine at a temperature of about 85 ° C in the presence of nitric acid as an oxidizing agent in acetic and sulfuric acids at a molar ratio of iodine, benzene and nitric acid is 1: 3.5: 4. The output of iodobenzene.

The disadvantages of this method are the low yield of the target product due to the formation of a significant amount of nitro compounds and diiodobenzene, as well as the relatively low purity of the target product, since the latter is contaminated with decomposition products of iodobenzene.

In order to eliminate these drawbacks, increase the yield and improve the quality of the target product, it is proposed to conduct the process at 40-50 ° C, with a molar ratio of iodine, benzene and nitric acid 1: 2: 1.

The proposed method provides an increase in the yield of iodobenzene, since at a molar ratio of iodine: beizole: nitric acid 1: 2: 1, the formation of nitro compounds as by-products is excluded.

At 40-50 ° C, the formation of diiodobenzene is minimized. Reaction temperature

above 50 ° C contributes to the formation of diiodobenzene.

The absence of appreciable amounts of by-products makes it possible to significantly reduce and unstitch the process of separating pure iodobenzene from the reaction mixture. Isolation of the desired product in pure form was carried out in almost one operation — one-time distillation in vacuum.

The proposed method is as follows.

Nitric acid was gradually added to a mixture of benzene, iodine, acetic and sulfuric acids at a rate of 4 l / h, and a temperature of 40-50 ° C was added. Iodine, benzene and nitric acid are taken at a molar ratio of 1: .2: 1. The molar ratio of iodine: acetic acid: sulfuric acid is 1: 5: 1.

Upon completion of the reaction, the mixture is incubated for 1 hour at 40-50 ° C (to complete the reaction), cooled, the resulting heavy liquid is separated, washed with 10% sodium hydroxide solution and water, followed by distillation of technical iodbeizol under vacuum.

The yield of iodobenzene, calculated on benzene, is 80% (from the theoretically possible).

Content of the main substance is not less than 99% (99.6%).

Pure iodobenzene is stored under a layer of crystalline sodium sulphite for stabilization purposes.

Example. 45.2 kg of 100% acetic acid is sucked into the reactor. Under stirring, 20.6 of 100% sulfuric acid and 23 kg of 100% benzene are sucked in, 34.4 kg of 100% finely crushed iodine is charged through the hatch.

9.2 kg of 100% nitric acid is sucked into the measuring device. Fag the reaction mass in the reactor to 50 ° C. At this temperature, the addition of nitric acid from the measuring device to the reactor begins. The rate of addition is 5 l / h. During the addition, the reactor is cooled at a rate of 3 ° C per hour, gradually lowering the temperature of the mass to 40 ° C. After adding the total amount of nitric acid, the temperature is raised to 50 ° C and maintained at this temperature for 1 hour.

After aging the mixture is stratified into 2 layers. The bottom layer in the amount of 40 kg is bloated 1 time with distilled water, 2 times with 10% sodium hydroxide solution and

1 time with distilled water until neutral.

The obtained technical product is distilled on a column with 3 theoretical plates. At 60-70 ° C (15 mmHg), the first fraction is distilled off, and at 70-75 ° C (15 mmHg), high-purity iodobenzene (99.6%) is collected. The yield of the target product, counting on benzene, is 80%.

d4 ° 1.82-1.83; pV ° 1.618-1.620; 760 mmHg v .; 187-188 ° C.

Subject invention

The method of obtaining iodobenzene by iodizing benzene with iodine at elevated temperature in the presence of nitric acid as an oxidizing agent in acetic and sulfuric acids, followed by isolation of the target product by known methods, characterized in that, in order to increase the yield and improve the quality of the target product, the process is carried out at 40 50 ° C at a molar ratio of iodine, benzene and nitric acid 1: 2: 1.