A method for indirectly electro-synthesizing 2,6-dichlorobenzonitrile using 2,6-dichlorobenzyl chloride as a raw material

Abstract

The present invention discloses a method for indirectly electro-synthesizing 2,6-dichlorobenzonitrile using 2,6-dichlorobenzyl chloride as a raw material. The method uses 2,6-dichlorobenzyl chloride as a raw material, ammonium carbonate as a stable nitrogen source, potassium nitrate as a supporting electrolyte, and potassium iodide, sodium iodide or tetrabutylammonium iodide as a medium for oxidation conversion to obtain 2,6-dichlorobenzonitrile. The reaction substrate of the present invention has a low cost and a wider source, simplifies the process synthesis route, and simplifies the process of hydrolyzing 2,6-dichlorobenzyl chloride to generate 2,6-dichlorobenzaldehyde and then generating 2,6-dichlorobenzonitrile into directly electro-synthesizing 2,6-dichlorobenzonitrile from 2,6-dichlorobenzyl chloride, which can ensure a high yield while reducing the reaction cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic electro - synthesis, and particularly relates to an electrochemical synthesis method of 2,6 - dichlorobenzonitrile. Background Art

[0002] 2,6 - Dichlorobenzonitrile (2,6 - DCBN) is the chemical name of the highly effective herbicide "dichlobenil", which is a colorless crystal. It is not only a highly effective herbicide itself, but also a synthetic intermediate for various herbicides and insecticides, and is also widely used in the synthesis of various pharmaceuticals, dyes, and polymer materials.

[0003] The commonly used industrial method for synthesizing 2,6 - dichlorobenzonitrile is the gas - phase ammoxidation method, which means that in the presence of a catalyst, the reactants react with ammonia and oxygen in the air to produce 2,6 - dichlorobenzonitrile through an ammoxidation reaction. Compared with the organic synthesis method, the gas - phase ammoxidation method has a simple process, relatively low energy consumption, less pollution, high product yield and purity, and is an ideal industrial method.

[0004] Currently, most of the processes for preparing 2,6 - dichlorobenzonitrile by the gas - phase ammoxidation method use 2,6 - dichlorotoluene as the raw material. However, 2,6 - dichlorotoluene has a high price, and a highly efficient catalyst is required during the reaction process. So far, no breakthrough has been made in China in terms of the highly efficient catalyst required for the reaction. In addition, the devices for ammoxidizing 2,6 - dichlorotoluene to 2,6 - dichlorobenzonitrile mostly use fluidized beds. For example, in Chinese Patent ZL97109006.8, due to the special structure of the fluidized bed, the fluidization quality of the materials in the reactor is poor, the product yield is low, the catalyst is easily consumed, and the production cost is high.

[0005] CN201810967597.5 discloses a method for preparing 2,6 - dichlorobenzonitrile using 2,6 - dichlorobenzyl chloride as the raw material. Using 2,6 - dichlorobenzyl chloride as the raw material as the reactant to produce 2,6 - dichlorobenzonitrile has a relatively low cost. The price of this raw material is less than half of that of 2,6 - dichlorotoluene and is very cheap, which is very suitable for large - scale industrial production. And compared with the process flow using 2,6 - dichlorotoluene as the raw material, this process is simpler and can greatly reduce the production cost. However, the selectivity and yield of this process are relatively low, and a large amount of catalyst is still required. The preparation of the catalyst requires three complex process steps: activating the precursor, preparing the semi - finished product, and activating the semi - finished product. Even under the best process conditions, the final product yield can only be maintained at about 80%.

[0006] Compared with traditional organic synthesis methods, electro-synthesis uses electrons as oxidation and reduction agents, features mild reaction conditions, high reaction selectivity, easy control, and does not require the additional addition of oxidation and reduction agents, which is conducive to the separation and purification of products. Electro-synthesis can be divided into two categories: direct electro-synthesis and indirect electro-synthesis. Among them, indirect electro-synthesis uses the efficient regeneration of the medium on the electrode surface, which can significantly reduce the dosage of oxidants or reductants. Moreover, the use of indirect electro-synthesis can effectively avoid the problem of high reaction potential of the substrate, which is not only conducive to reducing energy consumption and improving the selectivity of the reaction, but also conducive to a wider range of functional group compatibility.

[0007] CN202111597931.0 discloses a method for catalytic synthesis of 2,6-dichlorobenzonitrile by electrochemically in-situ generating CH3COOI. This patent avoids the use of industrial catalysts, but the selected reaction substrate is 2,6-dichlorobenzyl alcohol, which is obtained by chlorinating 2,6-dichlorotoluene to 2,6-dichlorobenzyl chloride and then hydrolyzing it. The raw material cost is high, and it is easy to oxidize and deteriorate, making it difficult to store. In addition, this reaction uses ammonium acetate as the reaction nitrogen source, and the CH3COOI generated electrochemically in-situ produces acetic acid in the subsequent reaction, which has a certain impact on the environment. Moreover, in order to regulate the acidity and alkalinity of the reaction system, an acid-binding agent needs to be added to neutralize the acetic acid generated by the reaction. The introduction of the acid-binding agent not only increases the production cost, but also increases the separation difficulty and makes it difficult to purify the product.

[0008] Therefore, the present invention proposes a method for indirectly electro-synthesizing 2,6-dichlorobenzonitrile using 2,6-dichlorobenzyl chloride as the reaction substrate and ammonium carbonate as the nitrogen source, and using the electrochemically in-situ generated I 2 as the medium for the indirect electro-synthesis route. The reaction substrate has a low cost and a wider source, simplifies the process synthesis route, and simplifies the process of generating 2,6-dichlorobenzonitrile from the hydrolysis of 2,6-dichlorobenzyl chloride to the direct electro-synthesis of 2,6-dichlorobenzonitrile from 2,6-dichlorobenzyl chloride, which can ensure a high yield while reducing the reaction cost. Summary of the Invention

[0009] Aiming at the problems and deficiencies of the prior art, the present invention provides a method for indirectly electro-synthesizing 2,6-dichlorobenzonitrile using 2,6-dichlorobenzyl chloride. The method of the present invention has a lower cost, more controllable production, and no by-products.

[0010] The present invention adopts the following technical solutions:

[0011] A method for indirectly electro-synthesizing 2,6-dichlorobenzonitrile using 2,6-dichlorobenzyl chloride as a raw material is to electrochemically oxidize I - ions in-situ at the anode to generate I 2The invention discloses a method for catalytically synthesizing 2,6-dichlorobenzonitrile. The method uses 2,6-dichlorobenzyl chloride as a raw material, ammonium carbonate as a stable nitrogen source, potassium nitrate as a supporting electrolyte, and uses potassium iodide, sodium iodide or tetrabutylammonium iodide as a medium for oxidative conversion. The method is specifically implemented according to the following steps: adding an electrolyte into an electrolytic cell, turning on an electrolytic power supply and magnetic stirring in a sealed electrolytic cell for reaction, controlling the magnetic stirring speed to be 500 rpm to 1500 rpm, the reaction temperature to be 40 to 80°C, and the reaction current density to be 10 to 17.5 mA cm -2 After the reaction is completed, the electrolytic cell is opened and 2,6-dichlorobenzonitrile is obtained through post-treatment;

[0012] The electrolytic cell is a diaphragmless electrolytic cell, 2,6-dichlorobenzyl chloride, ammonium carbonate, supporting electrolyte, medium and solvent A are fully mixed to obtain a mixture A, and the mixture A is added to the diaphragmless electrolytic cell as an electrolyte, and the working electrode and the counter electrode are independently made of platinum, graphite or lead electrodes;

[0013] Alternatively, the electrolytic cell is a diaphragm electrolytic cell, 2,6-dichlorobenzyl chloride, ammonium carbonate, a supporting electrolyte, a medium and a solvent B are fully mixed to obtain a mixture B, and the mixture B is added to the anode chamber of the diaphragm electrolytic cell as an anolyte, the supporting electrolyte is dissolved in a solvent C to obtain a solution C, and the solution C is added to the cathode chamber of the diaphragm electrolytic cell as a catholyte;

[0014] The solvent A, solvent B and solvent C are each independently selected from water or a mixed solvent of acetonitrile and water, wherein the volume ratio of acetonitrile to water in the mixed solvent of acetonitrile and water is 1-4:14-11;

[0015] In the mixture A or mixture B, the molar ratio of 2,6-dichlorobenzyl chloride to ammonium carbonate, supporting electrolyte and medium is 1:20-40:1-2:1-8, and the ratio of 2,6-dichlorobenzyl chloride to solvent A or B is 1mmol:10-15ml respectively.

[0016] In the present invention, ammonium carbonate is used as a nitrogen source to react with the benzyl group in 2,6-dichlorobenzyl chloride to generate an imine group. In the mixture A, the molar ratio of 2,6-dichlorobenzyl chloride to ammonium carbonate is 1:20-40, preferably 1:30-40, and most preferably 1:40.

[0017] In the present invention, potassium nitrate is a supporting electrolyte, which can improve the conductivity of the solution. In the mixture A, the molar ratio of 2,6-dichlorobenzyl chloride to potassium nitrate is 1:1-2, preferably 1:1.5-2, and most preferably 1:1.5.

[0018] In the present invention, iodine salts such as potassium iodide are used as media. - Oxidized at the anode to generate I 2 , I2 It can displace the hydrogen on the amino group and then eliminate one molecule of hydrogen iodide to generate a cyano group. In the mixture A, the molar ratio of 2,6-dichlorobenzyl chloride to the medium is 1:1 - 8, preferably 1:6 - 8, and most preferably 1:8.

[0019] In the present invention, the solvent A, solvent B and solvent C preferably use a mixed solvent of acetonitrile and water. Preferably, the volume ratio of acetonitrile to water is 1 - 2:14 - 13, and most preferably, in the mixed solvent of acetonitrile and water, the volume ratio of acetonitrile to water is 1:14.

[0020] In the present invention, it is particularly preferred that in the mixture A or mixture B, the molar ratio of 2,6-dichlorobenzyl chloride to ammonium carbonate, potassium nitrate, and the medium is 1:20 - 40:1.5 - 2:1 - 8, and most preferably, the molar ratio of 2,6-dichlorobenzyl chloride to ammonium carbonate, supporting electrolyte, and the medium is 1:40:1.5:8.

[0021] In the present invention, when using a diaphragm electrolytic cell, the catholyte is the solution C prepared from a supporting electrolyte and solvent C. The supporting electrolyte is potassium nitrate. In the solution C, the concentration of the supporting electrolyte is 0.05 - 0.2 mol / L, preferably 0.1 - 0.2 mol / L, and most preferably 0.1 mol / L.

[0022] In the present invention, the working electrode and the counter electrode independently adopt a platinum, graphite or lead electrode, preferably a platinum or graphite electrode, and most preferably platinum as the working electrode and the counter electrode.

[0023] In the present invention, the electrolytic cell can be a diaphragm-free electrolytic cell or a diaphragm electrolytic cell. To reduce energy consumption, a diaphragm-free electrolytic cell is preferred. In the present invention, the reaction in the electrolytic cell is carried out under magnetic stirring, and the magnetic stirring speed is 500 rpm - 1500 rpm, preferably 800 rpm - 1200 rpm, and most preferably 1000 rpm. The reaction current density is 10 - 17.5 mA·cm -2 , preferably the reaction current density is 12 - 17.5 mA·cm -2 , and most preferably the reaction current density is 15 mA·cm -2 . The reaction temperature is 40 - 80 °C, preferably the reaction temperature is 40 - 60 °C, and most preferably the reaction temperature is 60 °C. The reaction time is 2 h - 8 h, preferably 5 - 6 h, and most preferably 6 h.

[0024] It is particularly preferred in the present invention that the reaction is carried out in a diaphragm-free electrolytic cell, and the reaction conditions are controlled as follows: the reaction temperature is 60 °C, the magnetic stirring speed is 1000 rpm, and the constant current electrolysis current density is set at 15 mA·cm -2 , and the reaction time is 6 h.

[0025] The post-treatment in the present invention is as follows: The reaction mixture is obtained as 2,6-dichlorobenzonitrile after rotary evaporation, extraction for desalting, and then rotary evaporation. Specifically, it is carried out according to the following steps: After the reaction ends, the reaction solution is rotary evaporated to dry the solvent, then sodium bisulfite and water are added and stirred and mixed for a while to remove the unreacted 2,6-dichlorobenzyl chloride. Then 1,2-dichloroethane is added for mixed extraction. After liquid separation, the water layer is removed. Then the remaining organic solution is rotary evaporated to dry the solvent to obtain the product.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. Compared with the reactions using 2,6-dichlorotoluene as the raw material in early literature, the reaction conditions of the present invention are simpler, shortening the reaction route; adopting the indirect electrochemical synthesis method, the requirements for reaction equipment are low, the synthesis can be achieved at a lower temperature, and the reaction efficiency is high and the reaction time is short. At the same time, the use of toxic and harmful cyanides as the reaction nitrogen source is avoided, reducing pollution.

[0028] 2. Compared with the reactions using 2,6-dichlorobenzaldehyde as the substrate and ammonium acetate as the nitrogen source in recent literature, the present invention uses 2,6-dichlorobenzyl chloride, which is cheaper and more widely sourced, as the reaction substrate. The use of an acid-binding agent is avoided during the process, which can reduce the reaction cost to a certain extent, simplify the reaction route, and achieve green synthesis.

[0029] 3. Compared with the synthesis of nitrile reactions using iodine as the medium in recent years, the present invention realizes the cyclic regeneration of iodine through the electrochemical method, greatly reducing the solvent amount, significantly reducing the difficulty of industrial production, and reducing the reaction cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a reaction device for synthesizing 2,6-dichlorobenzonitrile of the present invention;

[0031] Figure 2 It is the characterization mass spectrum of the intermediate obtained by reacting for 4 h in Example 7;

[0032] Figure 3 It is the characterization mass spectrum of the product after purification in Example 7. DETAILED DESCRIPTION OF THE INVENTION

[0033] The following specific examples are used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto.

[0034] Example 1

[0035] In a diaphragmless electrolytic cell with a platinum working electrode and a platinum counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 1.92 g of ammonium carbonate, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and a solvent (1 mL of acetonitrile and 14 mL of deionized water) were added. After ultrasonic dissolution, the electrolytic cell was sealed. It was heated to 40 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the current density of constant current electrolysis was set at 10 mA·cm -2 , the reaction time was 6 h. During the electrolysis process, NH 4 + ions were electrochemically reduced at the cathode to generate NH 3 (2NH 4 + +2e - →2NH 3 +H 2 ). A moist red litmus paper was used as an indicator to verify that NH 3 was generated at the cathode; meanwhile, I - ions were electrochemically oxidized at the anode to generate I 2 (2I - →I 2 +2e - ). The fact that I 2 was generated was confirmed by the naked eye observing that the solution changed from transparent to yellow. After the electrolysis was completed, the product 2,6-dichlorobenzonitrile was extracted with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and analyzed for composition and yield by gas chromatography-mass spectrometry. By gas chromatography detection, the yield of 2,6-dichlorobenzonitrile was 48%.

[0036] Example 2

[0037] In a diaphragmless electrolytic cell with a platinum working electrode and a platinum counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 1.92 g of ammonium carbonate, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and a solvent (1 mL of acetonitrile and 14 mL of deionized water) were added. After ultrasonic dissolution, the electrolytic cell was sealed. It was heated to 60 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the current density of constant current electrolysis was set at 10 mA·cm -2 , the reaction time was 6 h. After the electrolysis was completed, the product 2,6-dichlorobenzonitrile was extracted with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and analyzed for composition and yield by gas chromatography-mass spectrometry. By gas chromatography detection, the yield of 2,6-dichlorobenzonitrile was 53%.

[0038] Example 3

[0039] In a diaphragmless electrolytic cell with a platinum working electrode and a platinum counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 1.92 g of ammonium carbonate, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and a solvent (2 mL of acetonitrile and 13 mL of deionized water) were added. After ultrasonic dissolution, the electrolytic cell was sealed. It was heated to 60 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the current density of constant current electrolysis was set at 10 mA·cm -2 , the reaction time was 6 h. After electrolysis, the product 2,6-dichlorobenzonitrile was extracted with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and put into a gas chromatograph-mass spectrometer to analyze the composition and yield. By gas chromatography detection, the yield of 2,6-dichlorobenzonitrile was 48%.

[0040] Example 4

[0041] In a diaphragmless electrolytic cell with a platinum working electrode and a platinum counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 1.92 g of ammonium carbonate, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and 15 mL of deionized water were added. After ultrasonic dissolution, the electrolytic cell was sealed. It was heated to 60 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the current density of constant current electrolysis was set at 10 mA·cm -2 , the reaction time was 6 h. After electrolysis, the product 2,6-dichlorobenzonitrile was extracted with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and put into a gas chromatograph-mass spectrometer to analyze the composition and yield. By gas chromatography detection, the yield of 2,6-dichlorobenzonitrile was 42%.

[0042] Example 5

[0043] In a diaphragmless electrolytic cell with a platinum working electrode and a platinum counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 3.84 g of ammonium carbonate, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and a solvent (1 mL of acetonitrile and 14 mL of deionized water) were added. After ultrasonic dissolution, the electrolytic cell was sealed. It was heated to 60 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the current density of constant current electrolysis was set at 10 mA·cm -2 , the reaction time was 6 h. After electrolysis, the product 2,6-dichlorobenzonitrile was extracted with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and put into a gas chromatograph-mass spectrometer to analyze the composition and yield. By gas chromatography detection, the yield of 2,6-dichlorobenzonitrile was 69%.

[0044] Example 6

[0045] In a diaphragmless electrolytic cell with a platinum working electrode and a platinum counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 3.84 g of ammonium carbonate, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and a solvent (1 mL of acetonitrile and 14 mL of deionized water) were added. After ultrasonic dissolution, the electrolytic cell was sealed. The temperature was raised to 60 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the current density of the constant current electrolysis was set at 12 mA·cm -2 , the reaction time was 6 h. After the electrolysis was completed, the product 2,6-dichlorobenzonitrile was extracted with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and put into a gas chromatography-mass spectrometry instrument to analyze the composition and yield. By gas chromatography detection, the yield of 2,6-dichlorobenzonitrile was 74%.

[0046] Example 7: Optimal Example

[0047] In a diaphragmless electrolytic cell with a platinum working electrode and a platinum counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 3.84 g of ammonium carbonate, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and a solvent (1 mL of acetonitrile and 14 mL of deionized water) were added. After ultrasonic dissolution, the electrolytic cell was sealed. The temperature was raised to 60 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the current density of the constant current electrolysis was set at 15 mA·cm -2 , the reaction time was 6 h. Samples were taken every 1 h during the reaction. The characterization mass spectrum of the reaction intermediate obtained after 4 h of reaction is shown in Figure 2 , the reaction solution obtained after 6 h of reaction was used to extract the product 2,6-dichlorobenzonitrile with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and put into a gas chromatography-mass spectrometry instrument to analyze the composition and yield. The results showed that the yield of 2,6-dichlorobenzonitrile was 81%. After the electrolysis was completed, the reaction solution was rotary evaporated to dry the solvent, then 0.42 g of sodium bisulfite and 10 ml of water were added, stirred and mixed for a while, then 20 ml of 1,2-dichloroethane was added for mixed extraction and separation to remove the water layer, and then the remaining organic solution was rotary evaporated to dry the solvent to obtain the product. The characterization mass spectrum of the product is shown in Figure 3 .

[0048] Example 8:

[0049] In a diaphragmless electrolytic cell with a platinum working electrode and a platinum counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 3.84 g of ammonium carbonate, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and a solvent (1 mL of acetonitrile and 14 mL of deionized water) were added. After ultrasonic dissolution, the electrolytic cell was sealed. The temperature was raised to 60 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the current density of the constant current electrolysis was set at 17.5 mA·cm -2, the reaction time was 6 h. After electrolysis was completed, the product 2,6-dichlorobenzonitrile was extracted with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and put into a gas chromatography-mass spectrometry instrument to analyze the components and yield. By gas chromatography detection, the yield of 2,6-dichlorobenzonitrile was 72%.

[0050] Example 9

[0051] In a diaphragm-free electrolytic cell with a graphite working electrode and a platinum counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 3.84 g of ammonium carbonate, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and a solvent (1 mL of acetonitrile and 14 mL of deionized water) were added. After ultrasonic dissolution, the electrolytic cell was sealed. It was heated to 60 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the current density of constant current electrolysis was set to 15 mA〃cm -2 , the reaction time was 6 h. After electrolysis was completed, the product 2,6-dichlorobenzonitrile was extracted with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and put into a gas chromatography-mass spectrometry instrument to analyze the components and yield. By gas chromatography detection, the yield of 2,6-dichlorobenzonitrile was 63%.

[0052] Example 10

[0053] In a diaphragm-free electrolytic cell with a platinum working electrode and a graphite counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 3.84 g of ammonium carbonate, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and a solvent (1 mL of acetonitrile and 14 mL of deionized water) were added. After ultrasonic dissolution, the electrolytic cell was sealed. It was heated to 60 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the current density of constant current electrolysis was set to 15 mA〃cm -2 , the reaction time was 6 h. After electrolysis was completed, the product 2,6-dichlorobenzonitrile was extracted with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and put into a gas chromatography-mass spectrometry instrument to analyze the components and yield. By gas chromatography detection, the yield of 2,6-dichlorobenzonitrile was 58%.

[0054] Example 11: Diaphragm electrolytic cell

[0055] In a diaphragm electrolytic cell with a platinum working electrode and a platinum counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 3.84 g of ammonium carbonate, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and a solvent (1 mL of acetonitrile and 14 mL of deionized water) were added to the anodic cell, and 0.1 mol / L KNO prepared with potassium nitrate, 1 mL of acetonitrile and 14 mL of water was added to the cathodic cell 3An aqueous solution was ultrasonically dissolved and then the electrolytic cell was sealed. It was heated to 60 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the current density of constant current electrolysis was set at 15 mA·cm -2 , the reaction time was 6 h. After electrolysis was completed, the product 2,6-dichlorobenzonitrile was extracted with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and put into a gas chromatography-mass spectrometry instrument to analyze the composition and yield. After gas chromatography detection, the yield of 2,6-dichlorobenzonitrile was 76%.

[0056] Comparative Example 1: Potassium iodide was not added

[0057] In a diaphragm-free electrolytic cell with a platinum working electrode and a counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 3.84 g of ammonium carbonate, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and a solvent (1 mL of acetonitrile and 14 mL of deionized water) were added. After ultrasonic dissolution, the electrolytic cell was sealed. It was heated to 60 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the current density of constant current electrolysis was set at 15 mA·cm -2 , the reaction time was 6 h. After electrolysis was completed, the product 2,6-dichlorobenzonitrile was extracted with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and put into a gas chromatography-mass spectrometry instrument to analyze the composition and yield. After gas chromatography detection, the yield of 2,6-dichlorobenzonitrile was 1%.

[0058] Comparative Example 2: Ammonium carbonate was not added

[0059] In a diaphragm-free electrolytic cell with a platinum working electrode and a counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and a solvent (1 mL of acetonitrile and 14 mL of deionized water) were added. After ultrasonic dissolution, the electrolytic cell was sealed. It was heated to 60 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the current density of constant current electrolysis was set at 15 mA·cm -2 , the reaction time was 6 h. After electrolysis was completed, the product 2,6-dichlorobenzonitrile was extracted with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and put into a gas chromatography-mass spectrometry instrument to analyze the composition and yield. After gas chromatography detection, the yield of 2,6-dichlorobenzonitrile was 0%.

[0060] Comparative Example 3: No electricity was applied

[0061] In a diaphragmless electrolytic cell with a platinum working electrode and a platinum counter electrode, 0.195 g of 2,6-dichlorobenzyl chloride, 3.84 g of ammonium carbonate, 1.328 g of potassium iodide, 0.151 g of potassium nitrate and a solvent (1 mL of acetonitrile and 14 mL of deionized water) were added. After ultrasonic dissolution, the electrolytic cell was sealed. The temperature was raised to 60 °C in a water bath, the magnetic stirring speed was 1000 rpm, and the reaction time was 6 h. After electrolysis, the product 2,6-dichlorobenzonitrile was extracted with 1,2-dichloroethane. 200 μL of the extract was taken, and then 1000 μL of 1,2-dichloroethane was added and analyzed for composition and yield by gas chromatography-mass spectrometry. After gas chromatography detection, the yield of 2,6-dichlorobenzonitrile was 0%.

Claims

1. A method for indirectly electro-synthesizing 2,6-dichlorobenzonitrile using 2,6-dichlorobenzyl chloride as a raw material, characterized in that: Using 2,6-dichlorobenzyl chloride as the raw material, ammonium carbonate as the stable nitrogen source, potassium nitrate as the supporting electrolyte, and potassium iodide, sodium iodide or tetrabutylammonium iodide as the medium for oxidation conversion, the specific steps are as follows: Add the electrolyte solution into the electrolytic cell, turn on the electrolysis power supply and magnetic stirring in the sealed electrolytic cell for reaction, the magnetic stirring speed is 500 rpm to 1500 rpm, the reaction temperature is 40 to 80 °C, and the reaction current density is 10 to 17.5 mA·cm -2 , after the reaction is completed, open the electrolytic cell, and obtain 2,6-dichlorobenzonitrile through post-treatment; The electrolytic cell is a diaphragmless electrolytic cell. 2,6-dichlorobenzyl chloride, ammonium carbonate, a supporting electrolyte, a mediator and a solvent A are fully mixed to obtain a mixture A, and the mixture A is added to the diaphragmless electrolytic cell as an electrolyte solution. The working electrode and the counter electrode independently adopt platinum, graphite or lead electrodes; Or the electrolytic cell is a diaphragm electrolytic cell. 2,6-dichlorobenzyl chloride, ammonium carbonate, a supporting electrolyte, a mediator and a solvent B are fully mixed to obtain a mixture B, and the mixture B is added to the anode chamber of the diaphragm electrolytic cell as an anolyte. The supporting electrolyte is dissolved in a solvent C to obtain a solution C, and the solution C is added to the cathode chamber of the diaphragm electrolytic cell as a catholyte; The solvent A, solvent B and solvent C are independently selected from water or a mixed solvent of acetonitrile and water. In the mixed solvent of acetonitrile and water, the volume ratio of acetonitrile to water is 1-4:14-11; In the mixture A or mixture B, the molar ratio of 2,6-dichlorobenzyl chloride to ammonium carbonate, the supporting electrolyte, and the mediator is 1:20-40:1-2:1-8, and the ratio of 2,6-dichlorobenzyl chloride to solvent A or B is 1 mmol:10-15 ml respectively.

2. The method according to claim 1, characterized in that: In the mixture A, the molar ratio of 2,6-dichlorobenzyl chloride to ammonium carbonate is 1:30-40; the molar ratio of 2,6-dichlorobenzyl chloride to potassium nitrate is 1:1.5-2; the molar ratio of the feed of 2,6-dichlorobenzyl chloride to the mediator is 1:6-8.

3. The method according to claim 2, characterized in that: In the mixture A, the molar ratio of 2,6-dichlorobenzyl chloride to ammonium carbonate is 1:

40.

4. The method according to claim 2, characterized in that: In the mixture A, the molar ratio of 2,6-dichlorobenzyl chloride to potassium nitrate is 1:1.

5.

5. The method according to claim 2, characterized in that: In the mixture A, the molar ratio of the feed of 2,6-dichlorobenzyl chloride to the mediator is 1:

8.

6. The method according to claim 1, characterized in that: The solvent A, solvent B and solvent C use a mixed solvent of acetonitrile and water, and the volume ratio of acetonitrile to water is 1-2:14-13.

7. The method according to claim 6, characterized in that: In the mixed solvent of acetonitrile and water, the volume ratio of acetonitrile to water is 1:

14.

8. The method according to claim 1, characterized in that: In the solution C, the concentration of the supporting electrolyte is 0.05-0.2 mol / L.

9. The method according to claim 8, characterized in that: In the solution C, the concentration of the supporting electrolyte is 0.1-0.2 mol / L.

10. The method according to claim 9, characterized in that: In the solution C, the concentration of the supporting electrolyte is 0.1 mol / L.

11. The method according to claim 1, characterized in that: The magnetic stirring speed is controlled to be 800 rpm - 1200 rpm.

12. The method according to claim 11, characterized in that: Control the magnetic stirring speed at 1000 rpm.

13. The method according to claim 1, characterized in that: Control the reaction current density to be 12 - 17.5 mA·cm -2 .

14. The method according to claim 13, characterized in that: Control the reaction current density to be 15 mA·cm -2 .

15. The method according to claim 1, characterized in that: Control the reaction temperature at 40 - 60 °C.

16. The method according to claim 15, characterized in that: Control the reaction temperature at 60 °C.

17. The method according to claim 1, characterized in that: Control the reaction time at 2 h - 8 h.

18. The method according to claim 17, characterized in that: Control the reaction time at 5 - 6 h.

19. The method according to claim 18, characterized in that: Control the reaction time at 6 h.

20. The method according to claim 1, characterized in that: The reaction is carried out in a diaphragmless electrolytic cell, and the reaction conditions are controlled as follows: the reaction temperature is 60 °C, the magnetic stirring speed is 1000 rpm, and the constant current electrolysis current density is set at 15 mA·cm -2 , and the reaction time is 6 h.

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