CN115613059A - Method for preparing 2, 6-dichlorobenzonitrile by indirect electrosynthesis with 2, 6-dichlorobenzyl chloride as raw material - Google Patents
Method for preparing 2, 6-dichlorobenzonitrile by indirect electrosynthesis with 2, 6-dichlorobenzyl chloride as raw material Download PDFInfo
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Abstract
The invention discloses a method for preparing 2, 6-dichlorobenzonitrile by indirect electrosynthesis of 2, 6-dichlorobenzonitrile as a raw material, wherein 2, 6-dichlorobenzonitrile is used as a raw material, ammonium carbonate is used as a stable nitrogen source, potassium nitrate is used as a supporting electrolyte, and potassium iodide, sodium iodide or tetrabutylammonium iodide are used as media for oxidation conversion to obtain the 2, 6-dichlorobenzonitrile. The method has the advantages of low reaction substrate cost and wider source, simplifies the process synthesis route, simplifies the process of generating the 2, 6-dichlorobenzaldehyde from the hydrolysis of the 2, 6-dichlorobenzyl chloride and then generating the 2, 6-dichlorobenzonitrile into the process of directly electrically synthesizing the 2, 6-dichlorobenzonitrile from the 2, 6-dichlorobenzyl chloride, reduces the reaction cost and can ensure higher yield.
Description
Technical Field
The invention belongs to the technical field of organic electro-synthesis, and particularly relates to an electrochemical synthesis method of 2, 6-dichlorobenzonitrile.
Background
2, 6-dichlorobenzonitrile (2, 6-DCBN) is the chemical name of the highly effective herbicide dichlobenil, and is colorless crystalline. It is not only a highly effective herbicide, but also a synthetic intermediate of various herbicides and pesticides, and is widely used for synthesizing various medicines, dyes and high molecular materials.
A commonly used industrial method for synthesizing 2, 6-dichlorobenzonitrile is a gas phase ammoxidation method, which means that reactants and ammonia gas and oxygen in the air are subjected to ammoxidation reaction under the action of a catalyst to generate the 2, 6-dichlorobenzonitrile. Compared with the organic synthesis method, the gas phase ammoxidation method has the advantages of simple process, relatively low energy consumption, little pollution and high product yield and purity, and is an ideal method for industrialization.
At present, 2, 6-dichlorotoluene is mostly used as a raw material in the process of preparing 2, 6-dichlorobenzonitrile by adopting a gas phase ammoxidation method, but the price of the 2, 6-dichlorotoluene is high, and a high-efficiency catalyst is required to be used in the reaction process, so that no breakthrough is made in the aspect of the high-efficiency catalyst required by the reaction at home at present. In addition, the device for preparing 2, 6-dichlorobenzonitrile by ammoxidation using 2, 6-dichlorotoluene as a raw material mostly adopts a fluidized bed, for example, chinese patent ZL97109006.8, due to the special structure of the fluidized bed, the fluidized state quality of materials in the reactor is poor, the product yield is low, the catalyst is easy to lose, and the production cost is high.
CN201810967597.5 discloses a method for preparing 2, 6-dichlorobenzonitrile from 2, 6-dichlorobenzyl chloride, wherein the cost of producing 2, 6-dichlorobenzonitrile from 2, 6-dichlorobenzyl chloride as a raw material is relatively low, the price of the raw material is less than half of that of 2, 6-dichlorotoluene, the raw material is very cheap, and is very suitable for large-scale industrial production, and compared with a process flow using 2, 6-dichlorotoluene as a raw material, the process flow is simpler, and the production cost can be greatly reduced. However, the process has low selectivity and yield, still needs a large amount of catalysts, and the preparation of the catalysts needs to go through three complex processes of activating precursors, preparing semi-finished products and activating the semi-finished products, so that the final product yield can only be maintained at about 80 percent even under the optimal process conditions.
Compared with the traditional organic synthesis method, the electrosynthesis method takes electrons as the redox agent, has mild reaction conditions, high reaction selectivity and easy control, does not need to additionally add the redox agent, and is beneficial to separation and purification of products. Electrosynthesis methods can be divided into direct electrosynthesis and indirect electrosynthesis. The indirect electrosynthesis method utilizes efficient regeneration of a medium on the surface of an electrode, can obviously reduce the dosage of an oxidant or a reducing agent, can effectively avoid the problem of high reaction potential of a substrate by adopting the indirect electrosynthesis method, is favorable for reducing energy consumption, improves the selectivity of reaction and is also favorable for wider functional group compatibility.
CN202111597931.0 discloses a method for synthesizing 2, 6-dichlorobenzonitrile by electrochemical in-situ generation of CH3COOI catalysis, which avoids the use of industrial catalysts, but the reaction substrate selected in the method is 2, 6-dichlorobenzyl alcohol, 2, 6-dichlorobenzyl chloride is obtained by chlorination of 2, 6-dichlorotoluene and then hydrolysis, and the method has the advantages of high raw material cost, easy oxidative deterioration and difficult storage. In addition, ammonium acetate is used as a reaction nitrogen source in the reaction, acetic acid is generated in the subsequent reaction of CH3COOI generated in situ by electrochemistry, a certain degree of influence is caused on the environment, an acid-binding agent is required to be added for regulating and controlling the pH value of a reaction system to neutralize the acetic acid generated by the reaction, the introduction of the acid-binding agent not only can increase the production cost, but also can cause the increase of the separation difficulty and the difficulty in purifying the product.
Therefore, the invention provides I electrochemically generated in situ by taking 2, 6-dichlorobenzyl chloride as a reaction substrate and ammonium carbonate as a nitrogen source 2 Is a medium indirect electrosynthesis path. The reaction substrate has low cost and wider source, simplifies the process synthetic route, simplifies the process of generating 2, 6-dichlorobenzaldehyde from hydrolysis of 2, 6-dichlorobenzyl chloride and then generating 2, 6-dichlorobenzonitrile into the process of directly synthesizing the 2, 6-dichlorobenzonitrile from the 2, 6-dichlorobenzyl chloride, and can ensure higher yield while reducing the reaction cost.
Disclosure of Invention
Aiming at the problems and the defects of the prior art, the invention provides a method for preparing 2, 6-dichlorobenzonitrile by indirect electrosynthesis of 2, 6-dichlorobenzyl chloride, and the method has the advantages of lower cost, more controllable production and no by-product.
The invention adopts the following technical scheme:
a process for preparing 2, 6-dichlorobenzonitrile from 2, 6-dichlorobenzyl chloride by indirect electrosynthesis is disclosed, which comprises - In situ generation of ions by anodic electrochemical oxidation 2 The method for catalytically synthesizing the 2, 6-dichlorobenzonitrile takes 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, and is implemented according to the following steps: adding electrolyte into an electrolytic cell, starting an electrolytic power supply and magnetically stirring in the sealed electrolytic cell to react, controlling the magnetic stirring speed at 500-1500 rpm, the reaction temperature at 40-80 ℃, and the reaction current density at 10-17.5 mA "cm -2 Opening the electrolytic cell after the reaction is finished, and performing post-treatment to obtain 2, 6-dichlorobenzonitrile;
the electrolytic bath is a diaphragm-free electrolytic bath, 2, 6-dichlorobenzyl chloride, ammonium carbonate, supporting electrolyte, medium and solvent A are fully mixed to obtain a mixture A, the mixture A is added into the diaphragm-free electrolytic bath to be used as electrolyte, and a working electrode and a counter electrode respectively and independently adopt platinum, graphite or lead electrodes;
or the electrolytic cell is a diaphragm electrolytic cell, 2, 6-dichlorobenzyl chloride, ammonium carbonate, supporting electrolyte, medium and solvent B are fully mixed to obtain mixture B, the mixture B is added into an anode chamber of the diaphragm electrolytic cell to be used as anolyte, the supporting electrolyte is dissolved in solvent C to obtain solution C, and the solution C is added into a cathode chamber of the diaphragm electrolytic cell to be used as catholyte;
the solvent A, the solvent B and the solvent C are respectively and independently selected from water or a mixed solvent of acetonitrile and water, and in the mixed solvent of acetonitrile and water, the volume ratio of acetonitrile to water is 1-4;
in the mixture A or the mixture B, the molar ratio of the 2, 6-dichlorobenzyl chloride to the ammonium carbonate, the supporting electrolyte and the medium is 1-20-40, the ratio of the 2, 6-dichlorobenzyl chloride to the solvent A or B is respectively 1mmol.
In the invention, ammonium carbonate is used as a nitrogen source to react with benzyl in 2, 6-dichlorobenzyl chloride to generate imino. In the mixture A, the molar ratio of the 2, 6-dichlorobenzyl chloride to the ammonium carbonate is 1:40.
in the invention, potassium nitrate is used as a supporting electrolyte, so that the conductivity of the solution can be improved. In the mixture A, the molar ratio of the 2, 6-dichlorobenzyl chloride to the potassium nitrate is 1.
In the invention, iodine salt such as potassium iodide is used as a medium, I - Oxidized on the anode to form I 2 ，I 2 The hydrogen on the amino group can be replaced and then a molecule of hydrogen iodide is removed to form a cyano group. In the mixture A, the feeding molar ratio of the 2, 6-dichlorobenzyl chloride to the medium is 1:1 to 8, preferably 1:8.
in the present invention, a mixed solvent of acetonitrile and water is preferably used as the solvent a, the solvent B and the solvent C, and the volume ratio of acetonitrile to water is preferably 1 to 2.
In the mixture A or the mixture B, the molar ratio of the 2, 6-dichlorobenzyl chloride to the ammonium carbonate, the potassium nitrate and the medium is 1-20-40, 1-8, the most preferable molar ratio of the 2, 6-dichlorobenzyl chloride to the ammonium carbonate, the supporting electrolyte and the medium is 1.
In the present invention, when a diaphragm electrolytic cell is used, the catholyte is a solution C prepared from a supporting electrolyte and a solvent C, the supporting electrolyte is potassium nitrate, and the concentration of the supporting electrolyte in the solution C is 0.05 to 0.2mol/L, preferably 0.1 to 0.2mol/L, and most preferably 0.1mol/L.
In the present invention, the working electrode and the counter electrode are each independently a platinum, graphite or lead electrode, preferably a platinum or graphite electrode, and most preferably platinum is used as the working electrode and the counter electrode.
In the invention, the electrolytic cell can be a diaphragm-free electrolytic cell or a diaphragm electrolytic cell, and in order to reduce energy consumption,preference is given to diaphragm-free cells. In the present invention, the reaction in the electrolytic cell is carried out under magnetic stirring at a speed of 500 to 1500rpm, preferably 800 to 1200rpm, and most preferably 1000rpm. The reaction current density is 10-17.5 mA "cm -2 Preferably, the reaction current density is 12-17.5 mA "cm -2 Most preferably, the reaction current density is 15mA "cm -2 . The reaction temperature is 40 to 80 ℃, preferably 40 to 60 ℃, and most preferably 60 ℃. The reaction time is 2 to 8 hours, preferably 5 to 6 hours, and most preferably 6 hours.
According to the invention, the reaction is particularly preferably carried out in a diaphragm-free electrolytic cell under the following reaction conditions: the reaction temperature is 60 ℃, the magnetic stirring speed is 1000rpm, and the constant current electrolytic current density is set to be 15mA "cm -2 The reaction time is 6h.
The post-treatment of the invention comprises the following steps: the reaction mixture is subjected to rotary evaporation, extraction desalting and rotary evaporation to obtain the 2, 6-dichlorobenzonitrile, and the method specifically comprises the following steps: after the reaction is finished, the reaction solution is subjected to rotary evaporation and spin drying of the solvent, then sodium bisulfite and water are added, stirred, mixed and reacted for a while to remove unreacted 2, 6-dichlorobenzyl chloride, then 1, 2-dichloroethane is added for mixed extraction, the water layer is removed after liquid separation, and then the residual organic solution is subjected to rotary evaporation and spin drying of the solvent to obtain the product.
Compared with the prior art, the invention has the beneficial effects that:
1. compared with the reaction in which 2, 6-dichlorotoluene is used as a raw material in early literature, the reaction conditions are simpler, and the reaction route is shortened; the indirect electrochemical synthesis method has low requirements on reaction equipment, realizes synthesis at a lower temperature, and has high reaction efficiency and short reaction time. Meanwhile, the use of toxic and harmful cyanide as a reaction nitrogen source is avoided, and the pollution is reduced.
2. Compared with the reaction in which 2, 6-dichlorobenzaldehyde is used as a substrate and ammonium acetate is used as a nitrogen source in the documents in recent years, the method uses the 2, 6-dichlorobenzyl chloride which is cheaper and more widely available as a reaction substrate, avoids using an acid-binding agent in the process, can reduce the reaction cost to a certain extent, simplifies the reaction route, and realizes green synthesis.
3. Compared with the nitrile synthesis reaction using iodine as a medium in recent years, the method realizes the cyclic regeneration of iodine by an electrochemical method, greatly reduces the solvent amount, obviously reduces the difficulty of industrial production and reduces the reaction cost.
Drawings
FIG. 1 is a reaction apparatus for synthesizing 2, 6-dichlorobenzonitrile in accordance with the present invention;
FIG. 2 is a spectrum of the intermediate obtained in example 7 after 4h reaction;
FIG. 3 is a characteristic mass spectrum of the purified product of example 7.
Detailed Description
The following specific examples illustrate the technical aspects of the present invention, but the scope of the present invention is not limited thereto.
Example 1
In a diaphragm-free electrolytic cell using platinum as a working electrode and a counter electrode, 0.195g of 2, 6-dichlorobenzyl chloride, 1.92g of ammonium carbonate, 1.328g of potassium iodide, 0.151g of potassium nitrate and a solvent (1 mL of acetonitrile and 14mL of deionized water) were added, and the electrolytic cell was sealed after ultrasonic dissolution. Heating to 40 deg.C in water bath, magnetically stirring at 1000rpm, and constant current electrolyzing at 10mA "cm -2 Reaction time is 6h, NH in the electrolytic process 4 + Electrochemical reduction of ions at the cathode to form NH 3 (2NH 4 + +2e - →2NH 3 +H 2 ) The cathode is verified to have NH by using wet red litmus test paper as an indicator 3 Generating; at the same time I - Electrochemical oxidation of ions at the anode to form I 2 (2I - →I 2 +2e - ) Visual observation of the solution changed from clear to yellow confirmed that I 2 And (4) generating. After the electrolysis, the product 2, 6-dichlorobenzonitrile is extracted by 1, 2-dichloroethane, 200. Mu.L of extract is taken, then 1000. Mu.L of 1, 2-dichloroethane is added and put into a gas chromatograph-mass spectrometer for analysis of composition and yield, and the yield of 2, 6-dichlorobenzonitrile is 48% by gas chromatography detection.
Example 2
2,6-0.195g of dichlorobenzyl chloride, 1.92g of ammonium carbonate, 1.328g of potassium iodide and 0.151g of potassium nitrate solvent (1 mL of acetonitrile and 14mL of deionized water) are ultrasonically dissolved, and then the electrolytic cell is sealed. Heating to 60 deg.C in water bath, stirring with magnetic force at 1000rpm, and constant current electrolyzing with current density of 10mA "cm -2 The reaction time is 6h, after the electrolysis is finished, the product 2, 6-dichlorobenzonitrile is extracted by 1, 2-dichloroethane, 200 mu L of extract is taken, 1000 mu L of 1, 2-dichloroethane is added and put into a gas chromatograph-mass spectrometer for analysis of components and yield, and the yield of the 2, 6-dichlorobenzonitrile is 53% through gas chromatography detection.
Example 3
In a diaphragm-free electrolytic cell using platinum as a working electrode and a counter electrode, 0.195g of 2, 6-dichlorobenzyl chloride, 1.92g of ammonium carbonate, 1.328g of potassium iodide, 0.151g of potassium nitrate and a solvent (2 mL of acetonitrile and 13mL of deionized water) were added, and the electrolytic cell was sealed after ultrasonic dissolution. Heating to 60 deg.C in water bath, magnetically stirring at 1000rpm, and constant current electrolyzing at 10mA "cm -2 The reaction time is 6h, after the electrolysis is finished, the product 2, 6-dichlorobenzonitrile is extracted by 1, 2-dichloroethane, 200 mu L of extract is taken, 1000 mu L of 1, 2-dichloroethane is added and put into a gas chromatograph-mass spectrometer for analysis of components and yield, and the yield of the 2, 6-dichlorobenzonitrile is 48% through gas chromatography detection.
Example 4
In a diaphragm-free electrolytic cell using platinum as a working electrode and a counter electrode, 0.195g of 2, 6-dichlorobenzyl chloride, 1.92g of ammonium carbonate, 1.328g of potassium iodide, 0.151g of potassium nitrate and 15mL of deionized water were added, and the electrolytic cell was sealed after ultrasonic dissolution. Heating to 60 deg.C in water bath, magnetically stirring at 1000rpm, and constant current electrolyzing at 10mA "cm -2 The reaction time is 6h, after the electrolysis is finished, the product 2, 6-dichlorobenzonitrile is extracted by 1, 2-dichloroethane, 200 mu L of extract is taken, 1000 mu L of 1, 2-dichloroethane is added and put into a gas chromatograph-mass spectrometer for analysis of components and yield, and the yield of the 2, 6-dichlorobenzonitrile is 42% through gas chromatography detection.
Example 5
In a diaphragm-free electrolytic cell using platinum as a working electrode and a counter electrode, 0.195g of 2, 6-dichlorobenzyl chloride, 3.84g of ammonium carbonate and iodine were addedPotassium nitrate 1.328g, potassium nitrate 0.151g and solvent (1 mL acetonitrile and 14mL deionized water), and sealing the electrolytic cell after ultrasonic dissolution. Heating to 60 deg.C in water bath, magnetically stirring at 1000rpm, and constant current electrolyzing at 10mA "cm -2 The reaction time is 6h, after the electrolysis is finished, the product 2, 6-dichlorobenzonitrile is extracted by 1, 2-dichloroethane, 200 mu L of extract is taken, 1000 mu L of 1, 2-dichloroethane is added and put into a gas chromatograph-mass spectrometer for analysis of components and yield, and the yield of the 2, 6-dichlorobenzonitrile is 69% by gas chromatography detection.
Example 6
In a diaphragm-free electrolytic cell using platinum as a working electrode and a counter electrode, 0.195g of 2, 6-dichlorobenzyl chloride, 3.84g of ammonium carbonate, 1.328g of potassium iodide, 0.151g of potassium nitrate and a solvent (1 mL of acetonitrile and 14mL of deionized water) were added, and the electrolytic cell was sealed after ultrasonic dissolution. Heating to 60 deg.C in water bath, magnetically stirring at 1000rpm, and constant current electrolyzing at current density of 12mA "cm -2 The reaction time is 6h, after the electrolysis is finished, the product 2, 6-dichlorobenzonitrile is extracted by 1, 2-dichloroethane, 200 mu L of extract is taken, 1000 mu L of 1, 2-dichloroethane is added and put into a gas chromatograph-mass spectrometer for analysis of components and yield, and the yield of the 2, 6-dichlorobenzonitrile is 74% through gas chromatography detection.
Example 7: best mode for carrying out the invention
In a diaphragm-free electrolytic cell using platinum as a working electrode and a counter electrode, 0.195g of 2, 6-dichlorobenzyl chloride, 3.84g of ammonium carbonate, 1.328g of potassium iodide, 0.151g of potassium nitrate and a solvent (1 mL of acetonitrile and 14mL of deionized water) were added, and the electrolytic cell was sealed after ultrasonic dissolution. Heating to 60 deg.C in water bath, magnetically stirring at 1000rpm, and constant current electrolyzing at 15mA "cm -2 The reaction time is 6 hours, the reaction is sampled every 1 hour, the characterization mass spectrogram of a reaction intermediate product obtained after 4 hours of reaction is shown in figure 2, a reaction liquid obtained after 6 hours of reaction is extracted into a product 2, 6-dichlorobenzonitrile by using 1, 2-dichloroethane, 200 mu L of extract is taken, then 1000 mu L of 1, 2-dichloroethane is added and put into a gas chromatograph-mass spectrometer for analysis of components and yield, and the result shows that the yield of the 2, 6-dichlorobenzonitrile is 81%. After the electrolysis is finished, the reaction solution is subjected to rotary evaporation to remove the solvent, and then 0.42g of sodium bisulfite and 10ml of water are added to be stirredAfter stirring and mixing reaction for one time, adding 20ml of 1, 2-dichloroethane for mixing, extracting, separating and removing a water layer, and then carrying out rotary evaporation on the residual organic solution to remove the solvent to obtain a product, wherein a characteristic mass spectrogram of the product is shown in figure 3.
Example 8:
in a diaphragm-free electrolytic cell using platinum as a working electrode and a counter electrode, 0.195g of 2, 6-dichlorobenzyl chloride, 3.84g of ammonium carbonate, 1.328g of potassium iodide, 0.151g of potassium nitrate and a solvent (1 mL of acetonitrile and 14mL of deionized water) were added, and the electrolytic cell was sealed after ultrasonic dissolution. Heating to 60 deg.C in water bath, magnetically stirring at 1000rpm, and constant current electrolyzing at 17.5mA "cm -2 The reaction time is 6h, after the electrolysis is finished, the product 2, 6-dichlorobenzonitrile is extracted by 1, 2-dichloroethane, 200 mu L of extract is taken, 1000 mu L of 1, 2-dichloroethane is added and put into a gas chromatograph-mass spectrometer for analysis of components and yield, and the yield of the 2, 6-dichlorobenzonitrile is 72% through gas chromatography detection.
Example 9
In a diaphragm-free electrolytic cell using graphite as a working electrode and platinum as a counter electrode, 0.195g of 2, 6-dichlorobenzyl chloride, 3.84g of ammonium carbonate, 1.328g of potassium iodide, 0.151g of potassium nitrate and a solvent (1 mL of acetonitrile and 14mL of deionized water) were added, and the electrolytic cell was sealed after ultrasonic dissolution. Heating to 60 deg.C in water bath, magnetically stirring at 1000rpm, and constant current electrolyzing at 15mA "cm -2 The reaction time is 6h, after the electrolysis is finished, the product 2, 6-dichlorobenzonitrile is extracted by 1, 2-dichloroethane, 200 mu L of extract is taken, 1000 mu L of 1, 2-dichloroethane is added and put into a gas chromatograph-mass spectrometer for analysis of components and yield, and the yield of the 2, 6-dichlorobenzonitrile is 63% by gas chromatography detection.
Example 10
In a diaphragm-free electrolytic cell using platinum as a working electrode and graphite as a counter electrode, 0.195g of 2, 6-dichlorobenzyl chloride, 3.84g of ammonium carbonate, 1.328g of potassium iodide, 0.151g of potassium nitrate and a solvent (1 mL of acetonitrile and 14mL of deionized water) were added, and the electrolytic cell was sealed after ultrasonic dissolution. Heating to 60 deg.C in water bath, magnetically stirring at 1000rpm, and constant current electrolyzing at 15mA "cm -2 The reaction time is 6h, the product 2 is extracted by 1, 2-dichloroethane after the electrolysis is finished,and 6-dichlorobenzonitrile, wherein 200 mu L of the extract is taken, 1000 mu L of 1, 2-dichloroethane is added, and the mixture is put into a gas chromatograph-mass spectrometer for analysis of components and yield, and the yield of the 2, 6-dichlorobenzonitrile is 58% through gas chromatography detection.
Example 11: electrolytic cell with diaphragm
In a diaphragm electrolytic cell using platinum as a working electrode and a counter electrode, 0.195g of 2, 6-dichlorobenzyl chloride, 3.84g of ammonium carbonate, 1.328g of potassium iodide, 0.151g of potassium nitrate and a solvent (1 mL of acetonitrile and 14mL of deionized water) were added to an anode cell, and 0.1mol/LKNO prepared from potassium nitrate, 1mL of acetonitrile and 14mL of water was added to a cathode cell 3 Ultrasonic dissolving the water solution, and sealing the electrolytic cell. Heating to 60 deg.C in water bath, magnetically stirring at 1000rpm, and constant-current electrolyzing with current density of 15mA "cm -2 The reaction time is 6h, after the electrolysis is finished, the product 2, 6-dichlorobenzonitrile is extracted by 1, 2-dichloroethane, 200 mu L of extract is taken, 1000 mu L of 1, 2-dichloroethane is added and put into a gas chromatograph-mass spectrometer for analysis of components and yield, and the yield of the 2, 6-dichlorobenzonitrile is 76% through gas chromatography detection.
Comparative example 1: without addition of potassium iodide
In a diaphragm-free electrolytic cell using platinum as a working electrode and a counter electrode, 0.195g of 2, 6-dichlorobenzyl chloride, 3.84g of ammonium carbonate, 1.328g of potassium iodide, 0.151g of potassium nitrate and a solvent (1 mL of acetonitrile and 14mL of deionized water) were added, and the electrolytic cell was sealed after ultrasonic dissolution. Heating to 60 deg.C in water bath, magnetically stirring at 1000rpm, and constant-current electrolyzing with current density of 15mA "cm -2 The reaction time is 6h, after the electrolysis is finished, the product 2, 6-dichlorobenzonitrile is extracted by 1, 2-dichloroethane, 200 mu L of extract is taken, 1000 mu L of 1, 2-dichloroethane is added and put into a gas chromatograph-mass spectrometer for analysis of components and yield, and the yield of the 2, 6-dichlorobenzonitrile is 1% through gas chromatography detection.
Comparative example 2: no ammonium carbonate was added
In a diaphragm-free electrolytic cell using platinum as a working electrode and a counter electrode, 0.195g of 2, 6-dichlorobenzyl chloride, 1.328g of potassium iodide, 0.151g of potassium nitrate and a solvent (1 mL of acetonitrile and 14mL of deionized water) were dissolved by ultrasound, and the electrolytic cell was sealed. Heating to 60 deg.C in water bath, and magnetically stirringThe temperature is 1000rpm, and the current density of constant current electrolysis is set to be 15mA "cm -2 The reaction time is 6h, after the electrolysis is finished, the product 2, 6-dichlorobenzonitrile is extracted by 1, 2-dichloroethane, 200 mu L of extract is taken, 1000 mu L of 1, 2-dichloroethane is added and put into a gas chromatograph-mass spectrometer for analysis of components and yield, and the yield of the 2, 6-dichlorobenzonitrile is 0% by gas chromatography detection.
Comparative example 3: is not electrified
In a diaphragm-free electrolytic cell using platinum as a working electrode and a counter electrode, 0.195g of 2, 6-dichlorobenzyl chloride, 3.84g of ammonium carbonate, 1.328g of potassium iodide, 0.151g of potassium nitrate and a solvent (1 mL of acetonitrile and 14mL of deionized water) were added, and the electrolytic cell was sealed after ultrasonic dissolution. Heating to 60 ℃ in a water bath, magnetically stirring at 1000rpm, reacting for 6h, extracting the product 2, 6-dichlorobenzonitrile with 1, 2-dichloroethane after electrolysis, taking 200. Mu.L of the extract, adding 1000. Mu.L of 1, 2-dichloroethane, and analyzing the components and yield in a gas chromatograph-mass spectrometer, wherein the yield of the 2, 6-dichlorobenzonitrile is 0% by gas chromatography detection.
Claims (9)
1. A method for preparing 2, 6-dichlorobenzonitrile by indirect electrosynthesis of 2, 6-dichlorobenzyl chloride as a raw material is characterized by comprising the following steps: the method takes 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, and is specifically implemented according to the following steps: adding electrolyte into an electrolytic cell, starting an electrolytic power supply in the sealed electrolytic cell and carrying out magnetic stirring for reaction, controlling the magnetic stirring speed to be 500-1500 rpm, the reaction temperature to be 40-80 ℃, and the reaction current density to be 10-17.5 mA "cm -2 Opening the electrolytic cell after the reaction is finished, and performing post-treatment to obtain 2, 6-dichlorobenzonitrile;
the electrolytic cell is a diaphragm-free electrolytic cell, 2, 6-dichlorobenzyl chloride, ammonium carbonate, supporting electrolyte, medium and solvent A are fully mixed to obtain a mixture A, the mixture A is added into the diaphragm-free electrolytic cell to be used as electrolyte, and a working electrode and a counter electrode respectively and independently adopt platinum, graphite or lead electrodes;
or the electrolytic cell is a diaphragm electrolytic cell, 2, 6-dichlorobenzyl chloride, ammonium carbonate, supporting electrolyte, medium and solvent B are fully mixed to obtain a mixture B, the mixture B is added into an anode chamber of the diaphragm electrolytic cell to be used as anolyte, the supporting electrolyte is dissolved in solvent C to obtain solution C, and the solution C is added into a cathode chamber of the diaphragm electrolytic cell to be used as catholyte;
the solvent A, the solvent B and the solvent C are respectively and independently selected from water or a mixed solvent of acetonitrile and water, and in the mixed solvent of acetonitrile and water, the volume ratio of acetonitrile to water is 1-4;
in the mixture A or the mixture B, the molar ratio of the 2, 6-dichlorobenzyl chloride to the ammonium carbonate, the supporting electrolyte and the medium is 1-20 to 2, and the ratio of the 2, 6-dichlorobenzyl chloride to the solvent A or B is respectively 1mmol.
2. The method of claim 1, wherein: in the mixture A, the molar ratio of 2, 6-dichlorobenzyl chloride to ammonium carbonate is 1:40; the molar ratio of the 2, 6-dichlorobenzyl chloride to the potassium nitrate is 1.5-2, and the most preferable ratio is 1; the feeding molar ratio of the 2, 6-dichlorobenzyl chloride to the medium is 1:8.
3. the method of claim 1, wherein: the solvent A, the solvent B and the solvent C are mixed solvents of acetonitrile and water, the volume ratio of the acetonitrile to the water is 1-2.
4. The method of claim 1, wherein: the concentration of the supporting electrolyte in the solution C is 0.05 to 0.2mol/L, preferably 0.1 to 0.2mol/L, and most preferably 0.1mol/L.
5. The method of claim 1, wherein: the magnetic stirring speed is controlled to be 800rpm to 1200rpm, and the most preferable is 1000rpm.
6. The method of claim 1, wherein the method further comprises the step of removing the solvent from the mixtureIs characterized in that: controlling the reaction current density to be 12-17.5 mA "cm -2 Most preferably, the reaction current density is 15mA "cm -2 。
7. The method of claim 1, wherein: the reaction temperature is controlled to be 40-60 ℃, and the most preferable reaction temperature is 60 ℃.
8. The method of claim 1, wherein: the reaction time is controlled to be 2 to 8 hours, preferably 5 to 6 hours, and most preferably 6 hours.
9. The method of claim 1, wherein: the reaction is carried out in a diaphragm-free electrolytic cell, and the reaction conditions are controlled as follows: the reaction temperature is 60 ℃, the magnetic stirring speed is 1000rpm, and the constant current electrolytic current density is set to be 15mA "cm -2 The reaction time is 6h.
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