CN117362148A - Novel method for synthesizing trichlorobenzyl by photochlorination - Google Patents

Abstract

The invention relates to the technical field of organic synthesis, in particular to a novel method for synthesizing trichlorobenzyl by a photochlorination reaction, which comprises the following steps: s1, adding toluene or toluene and an organic solvent into a tubular reactor or a common reactor, heating to a preset reaction temperature, starting ultraviolet irradiation, slowly adding chlorine until the reaction is complete, and carrying out selective chlorination under the condition of ultraviolet irradiation to obtain a crude trichlorobenzyl product; s2, rectifying and separating the crude trichlorobenzyl product obtained by the reaction, and purifying to obtain a trichlorobenzyl finished product and a small amount of toluene. In the invention, the raw materials are cheap and easy to obtain, the whole synthesis reaction is simple in operation and post-treatment, benzyl plastic is not generated, the method is green and environment-friendly, the product quality and yield are improved, continuous mass production can be realized, unreacted raw materials can be recycled, the cost is reduced, the atomic economy in the synthesis method is in line with the green chemistry principle, and the synthesis method has better social benefit and economic benefit and is suitable for industrial production.

Description

A new method for synthesizing benzyl trichloride through photochlorination reaction

Technical field

The invention relates to the technical field of organic synthesis, specifically a new method for synthesizing benzyl trichloride through photochlorination reaction.

Background technique

Trichlorobenzyl, also known as trichlorotoluene, is a colorless and transparent liquid with a special pungent odor. The melting point is -5°C and the boiling point is 220.8°C. It is mainly replaced by toluene and chlorine through free radical chlorination under a free radical initiator. It is produced by reaction, smokes in the air, is unstable, and is easily hydrolyzed; trichlorobenzyl is mainly used as a raw material for dyes and pharmaceutical intermediates, and is used to manufacture benzoic acid, benzoyl chloride, Sanbenjia dyes, and anthracene Quinone dyes, quinoline dyes, and UV absorbers UV-9, UV-531, etc. Trichlorobenzyl is an important organic synthesis intermediate.

The traditional method is to carry out free radical chlorination substitution reaction between toluene and chlorine under the action of free radical initiator. However, this process has low conversion rate and difficult to control the chlorination depth, so it is easy to generate by-products such as benzyl monochloride and benzyl dichloride. The product, and as the chlorination deepens and the reaction temperature increases, more cyclic polychlorides are easily generated, which not only affects the yield, but also has a great impact on the subsequent separation and purification. In addition, during the production process In addition, due to the introduction of metals and compounds into the equipment or materials, the reaction cannot proceed normally in the early stage, generating a large amount of benzyl plastic, resulting in a large loss of materials.

In view of this, this application intends to propose a new method for synthesizing benzyl trichloride through photochlorination reaction to solve the above problems.

Contents of the invention

The purpose of the present invention is to provide a new method for synthesizing trichlorobenzyl through photochlorination reaction, aiming to solve the problems of high energy consumption, low reaction efficiency, low product conversion rate and purity, and pollution in existing trichlorobenzyl synthesis technologies. serious problem.

In order to achieve the above objects, the present invention provides the following technical solutions:

A new method for synthesizing benzyl trichloride through photochlorination reaction, including the following steps:

S1. Add toluene, or toluene and organic solvent to the tubular reactor or ordinary reactor, raise the temperature to the preset reaction temperature, turn on the ultraviolet illumination, and slowly pour in chlorine until the reaction is complete, and perform selective chlorination under ultraviolet illumination. to obtain crude trichlorobenzyl;

S2. Distillate and separate the crude trichlorobenzyl product obtained from the reaction, and purify to obtain the finished trichlorobenzyl product and a small amount of toluene.

The present invention is further configured as follows: in step S1, the reaction formula of the crude trichlorobenzyl is as follows:

The present invention is further configured as follows: in step S1, the molar ratio of toluene and chlorine is 1:1~1.3, the wavelength of the ultraviolet light is 300~400nm, and the reaction temperature is 65~180°C.

The present invention is further configured as follows: in step S1, the chlorination reaction does not use a solvent or the solvent used is acetic acid, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, alcohols , chloroform and acetonitrile, and the alcohol is methanol or ethanol isopropyl alcohol.

The present invention is further configured as follows: in step S1, the toluene flow rate is 1-100L/min, and the optimal flow rate is determined according to the relationship between the specific conditions of the equipment and the reaction yield.

The present invention is further configured as follows: in step S2, the chemical formula of the obtained product trichlorobenzyl is as follows:

The present invention is further configured such that in step S2, the toluene separated by rectification can be reused and continue to be used as raw material for photochlorination reaction.

Beneficial effects of the present invention:

1. In the present invention, by adding toluene or toluene and an organic solvent in a tubular reactor or an ordinary reactor, raising the temperature to the preset reaction temperature, turning on the ultraviolet light, and pouring in chlorine until the reaction is complete, the crude trichlorobenzyl product is obtained , the crude trichlorobenzyl obtained from the reaction is distilled and separated to obtain the finished trichlorobenzyl and a small amount of toluene. Toluene and chlorine are used as raw materials. The raw materials are cheap and easy to obtain. At the same time, the reaction will not produce benzyl plastic, which is green and environmentally friendly, and improves the product quality. quality and yield, reducing the difficulty of operation; in addition, the synthesis method is simple to operate and post-process, produces little pollution during the production process, can achieve continuous large-scale production, and unreacted raw materials can be reused, greatly reducing costs;

2. In the present invention, the atom economy in the synthesis method conforms to the principles of green chemistry, and the synthesis method has simple process operation, good social and economic benefits, and is suitable for industrial production;

3. In the present invention, in the synthesis method, the content of trichlorobenzyl can reach more than 99.7%, and the yield of trichlorobenzyl can reach more than 95.0%. The synthetic product has high content and good quality, which solves the problem of existing trichlorobenzyl synthesis. The technology has problems such as high energy consumption, low reaction efficiency, low product conversion rate and purity, and serious pollution.

Description of the drawings

Figure 1 is a method flow chart of a new method for synthesizing benzyl trichloride through photochlorination reaction of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Please refer to Figure 1, a new method for synthesizing benzyl trichloride through photochlorination reaction, including the following steps:

Step 1. Add toluene, or toluene and an organic solvent, into a tubular reactor or ordinary reactor, raise the temperature to the preset reaction temperature, turn on ultraviolet illumination, and slowly pour in chlorine until the reaction is complete, and perform selectivity under ultraviolet illumination. Chlorination gives crude trichlorobenzyl, and the reaction formula is as follows:

Among them, the molar ratio of toluene and chlorine in the raw material is 1:1 to 1.3, and the molar ratio of toluene and chlorine can also be 1:3.0, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5 , 1:3.6, 1:3.7, 1:3.8, 1:3.9; the wavelength of ultraviolet light is 300~400nm, and the wavelength of ultraviolet light can also be 300nm, 320nm, 340nm, 360nm, 380nm, 400nm; and the reaction temperature is 65 ~180℃, the reaction temperature can be 65℃, 75℃, 80℃, 90℃, 100℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃; The chlorination reaction does not use solvents or the solvents used are acetic acid, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, alcohols, chloroform and acetonitrile, and the alcohols are methanol or Ethanol and isopropyl alcohol; the toluene flow rate is 1-100L/min. The toluene flow rate can also be 1L/min, 10L/min, 20L/min, 40L/min, 50L/min, 100L/min. The optimal flow rate depends on the specific conditions of the equipment. The relationship between and reaction yield is determined;

Step 2: Distillate and separate the crude trichlorobenzyl obtained from the reaction, and purify to obtain the finished trichlorobenzyl and a small amount of toluene, and the chemical formula of the obtained product trichlorobenzyl is as follows:

Among them, the toluene separated by distillation can be reused and can continue to be used as raw material for photochlorination reaction. For example, the vacuum is turned on in the distillation tower, the condenser of the distillation tower is turned on, and the vacuum distillation separation is performed after heating.

Embodiment 1

Add 1200Kg toluene into the 3000L reaction kettle, raise the temperature to 65℃~70℃, turn on the ultraviolet light, the wavelength of the ultraviolet light is 345nm, and rush chlorine gas into the reaction kettle at a flow rate of 70L/min until the reaction is complete to obtain crude benzyl trichloride; The crude trichlorobenzyl product obtained from the reaction was distilled and separated to obtain 2424Kg of trichlorobenzyl finished product with a content of 99.8% and a yield of 95.1%, and 36Kg of toluene with a content of 99.9%. The toluene was reused.

Embodiment 2

Add 1400Kg toluene into the 300L reaction kettle, raise the temperature to 120℃~125℃, turn on the ultraviolet light, the wavelength of the ultraviolet light is 375nm, and rush chlorine gas into the reaction kettle at a flow rate of 60L/min until the reaction is complete to obtain crude benzyl trichloride; then The crude trichlorobenzyl obtained from the reaction was distilled and separated to obtain 2766.8Kg of finished trichlorobenzyl, with a content of 99.7%, and a yield of 93.0%, and 70Kg of toluene, with a content of 99.9%. The toluene was reused.

Embodiment 3

Turn on the heating system of the tubular reactor, raise the temperature to 90℃~100℃, turn on the ultraviolet light, the wavelength of the ultraviolet lamp is 400nm, turn on the toluene feed pump, pump toluene into the tubular reactor at a flow rate of 10L/min, and open the chlorine valve , inject chlorine gas at 6.5NM ³ /min and react for 3 hours to obtain crude trichlorobenzyl; then perform distillation and separation of the crude trichlorobenzyl obtained from the reaction to obtain 3168Kg of trichlorobenzyl finished product, with a content of 99.7% and a yield of 95.0%. Toluene 32Kg, content 99.9%, toluene reuse.

Embodiment 4

Turn on the heating system of the tubular reactor, raise the temperature to 85℃~90℃, turn on the ultraviolet light, the wavelength of the ultraviolet lamp is 370nm, turn on the toluene feed pump, pump toluene into the tubular reactor at a flow rate of 15L/min, and open the chlorine valve , inject chlorine gas at 9.8NM ³ /min and react for 2 hours to obtain crude trichlorobenzyl; then perform distillation and separation of the crude trichlorobenzyl obtained from the reaction to obtain 3180Kg of trichlorobenzyl finished product, with a content of 99.8% and a yield of 95.3%. Toluene 40Kg, content 99.9%, toluene reuse.

Comparative Example 1

Put 1300Kg toluene and 15Kg benzoyl peroxide into the 2000L reaction kettle, start stirring and slowly introduce chlorine gas at a temperature of 90-100°C. As the reaction proceeds, the temperature gradually increases. After 3 hours, increase the temperature to At 160-180°C, continue the chlorine reaction for 5 hours to obtain crude trichlorobenzyl; cool to 10-15°C, conduct distillation and separation of the crude trichlorobenzyl obtained from the reaction, and obtain 2348.1Kg of trichlorobenzyl, with a content of 99.3%. The rate is about 85.0%.

Comparative Example 2

Put 1400Kg toluene and 18Kg benzoyl peroxide into the 2000L reaction kettle, start stirring and slowly introduce chlorine gas at a temperature of 90-100°C. As the reaction proceeds, the temperature gradually increases. After 3 hours, increase the temperature to At 160-180°C, continue the chlorine reaction for 5 hours to obtain crude trichlorobenzyl; cool to 10-15°C, conduct distillation and separation of the crude trichlorobenzyl obtained from the reaction, and obtain 2469.2Kg of trichlorobenzyl, with a content of 99.4%. The rate is about 83.1%.

The specific effects of the examples and comparative examples are as shown in Table 1:

Table 1 Comparison of effects between embodiments and comparative examples

It can be seen from this that according to the solution provided by the present invention, the content of trichlorobenzyl can reach more than 99.7%, and the yield of trichlorobenzyl can reach more than 95.0%.

In the present invention, there is a new method for synthesizing trichlorobenzyl through photochlorination reaction. In the present invention, toluene, or toluene and an organic solvent are added to a tubular reactor or an ordinary reactor, the temperature is raised to the preset reaction temperature, and ultraviolet light is turned on. , flush chlorine gas until the reaction is complete, and obtain crude trichlorobenzyl. The crude trichlorobenzyl obtained by the reaction is distilled and separated to obtain finished trichlorobenzyl and a small amount of toluene, and the purified toluene can be directly reused. The reaction temperature The temperature is 65~180℃, the wavelength of ultraviolet light is 300~400nm, and the solvent is acetic acid, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, alcohols (methanol, ethanol, isopropyl alcohol etc.), chloroform, acetonitrile, etc., the toluene flow rate is 1-100L/min, and the molar ratio of toluene and chlorine is 1:3~3.9;

This new method of synthesizing trichlorobenzyl through photochlorination reaction uses toluene and chlorine as raw materials. The raw materials are cheap and easy to obtain. At the same time, the reaction will not produce benzyl plastic. It is green and environmentally friendly, improves product quality and yield, and reduces operation difficulty; in addition, the method The synthesis method is simple in the entire operation and post-processing, produces little pollution during the production process, can realize continuous large-scale production, and unreacted raw materials can be reused, greatly reducing costs; the atom economy in the synthesis method of the present invention is in line with green chemistry principle, and the synthesis method has simple process operation, good social and economic benefits, and is suitable for industrial production; at the same time, in the synthesis method of the present invention, the content of trichlorobenzyl can reach more than 99.7%, and the yield of trichlorobenzyl can Reaching more than 95.0%, the synthetic product has high content and good quality, and solves the problems of high energy consumption, low reaction efficiency, low product conversion rate and purity, and serious pollution existing in the existing trichlorobenzyl synthesis technology.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art will understand that various changes, modifications, and substitutions can be made to these embodiments without departing from the principles and spirit of the invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (7)

1. The novel method for synthesizing the trichlorobenzyl by the photochlorination reaction is characterized by comprising the following steps of:

s1, adding toluene or toluene and an organic solvent into a tubular reactor or a common reactor, heating to a preset reaction temperature, starting ultraviolet irradiation, slowly adding chlorine until the reaction is complete, and carrying out selective chlorination under the condition of ultraviolet irradiation to obtain a crude trichlorobenzyl product;

s2, rectifying and separating the crude trichlorobenzyl product obtained by the reaction, and purifying to obtain the product trichlorobenzyl and a small amount of toluene.

2. The novel method for synthesizing trichlorobenzyl by photochlorination according to claim 1, which is characterized in that: in step S1, the crude trichlorobenzyl product has the following reaction formula:

3. the novel method for synthesizing trichlorobenzyl by photochlorination according to claim 1, which is characterized in that: in the step S1, the molar ratio of toluene to chlorine is 1:1-1.3, the wavelength of ultraviolet light is 300-400 nm, and the reaction temperature is 65-180 ℃.

4. The novel method for synthesizing trichlorobenzyl by photochlorination according to claim 1, which is characterized in that: in step S1, the chlorination reaction does not use a solvent or uses acetic acid, tetrahydrofuran, N-dimethylformamide, N-dimethylacetamide, alcohols, chloroform and acetonitrile, and the alcohols are methanol or ethanol isopropanol.

5. The novel method for synthesizing trichlorobenzyl by photochlorination according to claim 1, which is characterized in that: in step S1, the flow rate of toluene is 1-100L/min, and the optimal flow rate is determined according to the relation between the specific condition of equipment and the reaction yield.

6. The novel method for synthesizing trichlorobenzyl by photochlorination according to claim 1, which is characterized in that: in step S2, the resulting product trichlorobenzyl has the formula:

7. the novel method for synthesizing trichlorobenzyl by photochlorination according to claim 1, which is characterized in that: in the step S2, toluene separated by rectification can be recycled and is continuously used as a raw material for photochlorination.