JP2000247941A - Production of bromoacetonitrile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a bromoacetonitrile useful as an intermediate for pharmaceuticals, agrochemicals, etc., accompanying little by-production of polyhalogenated compound by brominating acetonitrile in the presence of hydrogen chloride gas under light irradiation. SOLUTION: Hydrogen chloride gas is blown into a reaction system and thereafter bromine is made to react with acetonitrile under light irradiation. The amount of bromine is preferably 0.01-1 mol, more preferably 0.01-0.40 mol based on 1 mol of acetonitrile. The reaction is carried out preferably in the absence of solvent e.g. by blowing hydrogen chloride gas into an acetonitrile reaction system and dropping bromine into the system under light irradiation. The light is e.g. ultraviolet ray of 3,650-3,690 Å wavelength radiated from a 100 W high-pressure mercury lamp. The reaction temperature is preferably 30-80 deg.C, more preferably 65-75 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing bromoacetonitrile, which can produce bromoacetonitrile with a high yield without causing by-products of polyhalogen compounds by reacting acetonitrile and bromine under light irradiation. It is.

[0002]

2. Description of the Related Art Bromoacetonitrile is known as a useful intermediate for agricultural chemicals, medicines, etc., and its production method is known by the following formula (Bu).
lletein de la Sciete de Franse, {2} 47,400).

[0003]

(Equation 1)

Also, acetonitrile is mixed with chlorine and bromine in the gas phase,
There has been proposed a method of irradiating light at a temperature not higher than the boiling point of monobromoacetonitrile to recover the generated monobromoacetonitrile in a liquid state (JP-A-46-6893).

Further, a method has been proposed in which potassium bromide is added to chloroacetonitrile in a methanol solution, the mixture is refluxed for 1 to 24 hours, and chloroacetonitrile is halogen-exchanged with potassium bromide to obtain bromoacetonitrile. (JP-A-51-23219).

[0006]

THE INVENTION Problems to be Solved] However, the iodinated acetonitrile described above, information on how to brominating ICH 2 _CN obtained, the synthesis of ICH 2 _CN raw material is difficult, as an industrial production method Is not suitable.

Further, in the above-mentioned method of irradiating acetonitrile in the gas phase with light and introducing bromine gas by introducing chlorine and bromine gas and the method of obtaining bromoacetonitrile by halogen-exchanging ClCH ₂ CN in a methanol solution with KBr. Is disadvantageous in that BrCH ₂ CN and ClCH ₂ CN coexist and separation is difficult.

In addition, as a method for producing bromoacetonitrile, a method for producing BrCH ₂ CN by dehydrating BrCH ₂ CONH ₂ using P ₂ O ₅ has been proposed, but this method is toxic. Since P ₂ O ₅ is used, it is not an industrially good method.

In view of the above, the present inventors have conducted intensive studies for the purpose of developing a method for producing bromoacetonitrile with a high yield without generating any by-products. As a result, acetonitrile was irradiated with light in the presence of hydrochloric acid gas to obtain bromine. It has been found that the purpose is achieved by the conversion.

[0010]

SUMMARY OF THE INVENTION Based on the above findings, the present invention proposes a method for producing bromoacetonitrile by blowing hydrochloric acid gas into a reaction system and then reacting bromine with acetonitrile under light irradiation. .

That is, in the method according to the present invention, hydrochloric acid gas is blown into a reaction system of acetonitrile, and the reaction between bromine and acetonitrile is performed under light irradiation to produce bromoacetonitrile. To produce bromoacetonitrile.

Although the reaction mechanism in the method of the present invention is not always clear, it is converted into CH3CN.HCl by the action of hydrochloric acid on acetonitrile, and the bromine atom radical-transferred by light abstracts the hydrogen atom of the methyl group of acetonitrile. It is presumed that the cyanomethyl radical reacts with a bromine atom to form bromoacetonitrile.

In the present invention, the amount of bromine used is in the range of 0.01 to 1 mole, particularly preferably 0.01 to 0.40 mole, based on acetonitrile as a raw material.

The amount of hydrochloric acid gas blown into the reaction system is not particularly limited, but if blown too much, acetonitrile is hydrolyzed by an acid, resulting in a decrease in yield.

Further, in carrying out the present invention, an organic solvent such as chloroform and carbon tetrachloride which is used in a usual bromination reaction may be used, but the reaction can be carried out without any problem without using any solvent, so that industrial use is possible. Considering the aspect, it is preferable not to use a solvent.

The reaction is carried out by, for example, blowing hydrochloric acid gas into the acetonitrile reaction system and dropping bromine into the reaction system while irradiating light.

As the wavelength used for light irradiation, a wavelength is used which is such that bromine is radically transferred to bromine atoms.
For example, ultraviolet light in a wavelength range of 3650 to 3690 ° irradiated from a 100 W high-pressure mercury lamp can be used.

The reaction is carried out at a temperature in the range of 30 to 80 ° C., preferably in the range of 65 to 75 ° C., so that the amount of hydrogen halide dissolved in the solvent is minimized and the side reaction is minimized. Can be.

When the reaction temperature is higher than 80 ° C., bubbling of HBr becomes intense, causing inconvenience such as dropping of bromine together, and when the temperature is lower than 30 ° C.
HBr dissolves well in acetonitrile, which is also undesirable because it causes inconvenience, such as causing hydrolysis of acetonitrile.

The progress of the reaction is monitored by instrumental analysis, for example, gas chromatography. Removal of bromoacetonitrile from the reaction solution is performed, for example, by washing with water and then distilling.

[0021]

The present invention will be described below with reference to examples. Example 1 600 g of acetonitrile in a glass container for photoreaction having a capacity of 700 ml
Fill and replace the inside air with nitrogen while stirring. Then, hydrochloric acid gas was blown into the container, and the inside nitrogen was sufficiently replaced with hydrochloric acid gas.
The container is heated while irradiating the container with ultraviolet rays in a wavelength range of 0 to 3690 °.

Then, 350 g of bromine is dropped over a period of 3 hours and 40 minutes while the temperature in the container is in the range of 70 ± 5 ° C., and after the completion of the dropping, the temperature is kept at the same temperature for 2 hours and 30 minutes. After completion of the reaction, the reaction solution was washed with water, purified by distillation and 124 g of bromoacetonitrile (G.
C. Purity 96.6%). Yield 47.2% vs. charged bromine.

Example 2 Acetonitrile 2000 was placed in a glass container for photoreaction having a capacity of 2500 ml.
g, and replace the inside air with nitrogen while stirring. Then, hydrochloric acid gas was blown into the container, and the inside nitrogen was sufficiently replaced with hydrochloric acid gas.
The container is heated while irradiating the inside of the container with ultraviolet rays in the wavelength range of 650 to 3690Å.

Then, 1168 g of bromine is added dropwise over 7 hours while the temperature in the container is in the range of 70 ± 5 ° C., and after completion of the addition, the temperature is maintained at the same temperature for 1 hour and 30 minutes. After completion of the reaction, the reaction solution was washed with water, purified by distillation, and 281 g of bromoacetonitrile (G.
C. Purity 96.6%). The yield was 32.0% based on charged bromine.

[0025]

In summary, according to the present invention, bromoacetylnitrile can be produced in good yield with almost no by-products of polyhalogen compounds.

Claims (1)

[Claims] 1. A process for producing bromoacetonitrile, characterized by blowing hydrochloric acid gas into a reaction system and then reacting bromine with acetonitrile under light irradiation.