A method for indirect electrolytic synthesis of p-benzoquinone and its derivatives

Abstract

A method for the indirect electrolytic synthesis of p-benzoquinone and its derivatives belongs to the field of electrochemical green synthesis. This method mainly uses iron salts as electrocatalysts and water and dichloromethane as solvents to prepare p-benzoquinone and its derivatives via indirect electrooxidation. The electrochemical synthesis method for p-benzoquinone and its derivatives described in this invention can achieve a yield of up to 90%, requires inexpensive and simple reaction equipment, and allows for the recycling of the aqueous phase. It is inexpensive and suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical green synthesis. This invention relates to a method for electrochemically synthesizing p-benzoquinone and its derivatives using iron salts as electrocatalysts. Background Technology

[0002] p-Benzoquinone is a yellow crystalline solid. As an important chemical raw material, p-benzoquinone has various applications in the chemical industry. Currently, the preparation of p-benzoquinone is mainly achieved through methods such as the oxidation of aniline, phenol, benzene, and hydroquinone. The manganese dioxide oxidation of aniline is the most important industrial method for preparing p-benzoquinone. Under acidic conditions, manganese dioxide is used as the oxidant, and the product is obtained after a series of post-treatments. This method is mature, and most manufacturers in my country use this method to produce p-benzoquinone. However, this method consumes a lot of raw materials and generates a large amount of waste residue and waste liquid, causing serious environmental pollution, and the yield is low. The phenol oxidation method is relatively environmentally friendly. DuPont has a patent report showing that under high pressure conditions with ketone bromide as a catalyst, 78% p-benzoquinone can be obtained, but the yield decreases as the pressure decreases. This method has high equipment requirements and is more difficult to operate. Most methods for synthesizing p-benzoquinone from benzene use electrochemical methods. Zheng KL, Li XA, Ge F. Journal of Yanan University (Natural Science Edition), 2008, 27, 68. et al. used lead as the anode to electrochemically oxidize benzene to prepare p-benzoquinone under acidic conditions. However, this method resulted in low conversion rates, high energy consumption, low yields, and long reaction times, making it unsuitable for industrial production. Hydroquinone can be converted to p-benzoquinone under the action of chemical oxidants or electrochemical conditions. For example, Shanmugam et al. used platinum sheets as electrodes and sodium bromide as an electrocatalyst to prepare p-benzoquinone by electrolysis in a two-phase system of sulfuric acid aqueous solution and dichloromethane. While this electrochemical method can achieve yields exceeding 90%, it requires expensive platinum electrodes. Furthermore, because it uses bromide ions as an electrocatalyst, the bromine produced under electrochemical conditions not only severely corrodes the equipment but also results in significant losses during post-processing. Derikvand et al. (Fatemeh D, Franca B, Raimondo M. Journal of Catalysis, 2010, 271, 99.) used silver oxide as a catalyst to oxidize hydroquinone with hydrogen peroxide to prepare p-benzoquinone, but silver oxide is expensive and difficult to recycle. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a green and efficient synthetic process for preparing p-benzoquinone using hydroquinone as a raw material, ferric chloride as an electrocatalyst, and constant current electrolysis. The reaction route is as follows:

[0004]

[0005] The operation method of the present invention is as follows: using graphite as the anode and stainless steel as the cathode, water and dichloromethane are added as solvents in a single-chamber electrolytic cell, and hydroquinone, ferric chloride and hydrochloric acid are added to the aqueous phase. After being energized for a period of time at 0-40°C, the target product p-benzoquinone can be obtained through simple extraction and recrystallization.

[0006] The solvent is preferably a mixture of water and dichloromethane, with a volume ratio preferably of 1:1.

[0007] The reaction temperature is from room temperature to 40°C, preferably 40°C.

[0008] The catalysts mentioned above can be various iron and ferrous salts, with ferric chloride being preferred.

[0009] The reaction electrodes described above are preferably made of stainless steel or graphite.

[0010] The acid used in the above reaction is preferably concentrated hydrochloric acid with a mass percentage concentration of 37%.

[0011] The preferred amount of acid in the above reaction is 0.5 times the amount of hydroquinone added to the hydrochloric acid.

[0012] The current density of the above reaction is 10⁻⁵⁰ mA / cm². 2 Preferably 20-30 mA / cm 2 .

[0013] The charge applied to the above reaction is 2 F / mol to 5 F / mol, preferably 3.5 F / mol.

[0014] Compared with the prior art, the method of the present invention has the following advantages:

[0015] 1. The reaction involved in this invention is carried out in a single-chamber electrolytic cell, which is simple to operate and meets the needs of industrial production.

[0016] 2. Ferric chloride is inexpensive, and the aqueous phase can be reused without the need for additional catalysts, thus reducing production costs.

[0017] 3. The working electrode uses common and inexpensive graphite sheets and stainless steel, which greatly reduces the cost.

[0018] 4. The method of the present invention uses common industrial reagents and conventional production conditions. The reaction conditions are mild, and electrons are used as oxidants during the reaction, which is also a clean production process. Detailed Implementation

[0019] Example 1:

[0020] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane solvent of 1:1 (10 mL). A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 82%.

[0021] Example 2:

[0022] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 16.2 mg (0.1 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 68%.

[0023] Example 3:

[0024] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 80 mg (0.2 mmol) of ferric sulfate were added to a water:dichloromethane solution of 1:1 (10 mL), followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode, and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 3.5 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 76%.

[0025] Example 4:

[0026] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:1,2-dichloroethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 35%.

[0027] Example 5:

[0028] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and a nickel sheet as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 74%.

[0029] Example 6:

[0030] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane solution of 1:1 (10 mL), followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode, and graphite was used as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 65%.

[0031] Embodiment seven:

[0032] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane solvent of 1:1 (10 mL). A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 10°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 28%.

[0033] Example 8:

[0034] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane solvent of 1:1 (10 mL). A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 20°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 46%.

[0035] Example 9:

[0036] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane solvent of 1:1 (10 mL). A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 30°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 65%.

[0037] Example 10:

[0038] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode, and stainless steel as the cathode, at a current of 10 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 42%.

[0039] Example 11:

[0040] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane solvent of 1:1 (10 mL). A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 15 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 67%.

[0041] Example 12:

[0042] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane solvent of 1:1 (10 mL). A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 20 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 72%.

[0043] Example 13:

[0044] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane solvent of 1:1 (10 mL). A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 30 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 73%.

[0045] Example 14:

[0046] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane solvent of 1:1 (10 mL). A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 35 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 52%.

[0047] Example 15:

[0048] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 8 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode, and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 54%.

[0049] Example 16:

[0050] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane solution of 1:1 (10 mL), followed by 25 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode, and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 62%.

[0051] Example 17:

[0052] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 76%.

[0053] Example 18:

[0054] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 67 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 71%.

[0055] Example 19:

[0056] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 84 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 67%.

[0057] Example 20:

[0058] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 2 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 58%.

[0059] Example 21:

[0060] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 2.5 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 64%.

[0061] Example 22:

[0062] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 3 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 70%.

[0063] Example 23:

[0064] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 3.5 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 76%.

[0065] Example 24:

[0066] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 72%.

[0067] Example 25:

[0068] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 3.5 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 85%.

[0069] Example 26:

[0070] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 3 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 78%.

[0071] Example 27:

[0072] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 2 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 55%.

[0073] Example 28:

[0074] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 5 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 60%.

[0075] Example 29:

[0076] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 30°C. Electrolysis was stopped when the current applied reached 3.5 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 30%.

[0077] Example 30:

[0078] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 25.2 mg (0.2 mmol) of ferrous chloride were added to a water:dichloromethane solution of 1:1 (10 mL), followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode, and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 3.5 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 77%.

[0079] Example 31:

[0080] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 30.2 mg (0.2 mmol) of ferrous sulfate were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 3.5 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 66%.

[0081] Example 32:

[0082] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 25.2 mg (0.2 mmol) of manganese chloride were added to a water:dichloromethane solution of 1:1 (10 mL), followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode, and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 3.5 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 83%.

[0083] Example 33:

[0084] In a single-chamber electrolytic cell, 110 mg (1.0 mmol) of hydroquinone and 26.8 mg (0.2 mmol) of copper chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 3.5 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 42%.

[0085] Example 34:

[0086] In a single-chamber electrolytic cell, the aqueous phase from Example 25 was retained, and 110 mg (1.0 mmol) of hydroquinone and 5 mL of dichloromethane were added. A graphite sheet electrode was used as the anode, and stainless steel as the cathode, at 25 mA / cm². 2 Electrolysis was performed under constant current and stirring at 40°C. Electrolysis was stopped when the current reached 3.5 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 78%. This process was repeated four times, and the yield of p-benzoquinone remained between 70% and 80%, specifically 80%, 77%, 70%, and 71%, respectively. This indicates that the aqueous phase after electrolysis can also be directly reused.

[0087] Example 35:

[0088] In a single-chamber electrolytic cell, 6.6 g (60 mmol) of hydroquinone and 1.94 g (12 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (400 mL) solvent, followed by 2.3 mL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 4 F / mol. After simple extraction and recrystallization, the product p-benzoquinone was obtained. Yield: 82%.

[0089] Example 36:

[0090] In a single-chamber electrolytic cell, 160 mg (1.0 mmol) of 1,4-dihydroxynaphthalene and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane solution of 1:1 (10 mL), followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode, and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the flux reached 3.5 F / mol. The product, 1,4-naphthoquinone, was obtained by column chromatography. Yield: 58%.

[0091] Example 37:

[0092] In a single-chamber electrolytic cell, 124 mg (1.0 mmol) of 2-methyl-1,4-benzenediphenol and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane solvent of 1:1 (10 mL), followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode, and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the current applied reached 3.5 F / mol. The product, 2-methyl-1,4-benzoquinone, was obtained by column chromatography. Yield: 80%.

[0093] Example 38:

[0094] In a single-chamber electrolytic cell, 138 mg (1.0 mmol) of 2,6-dimethyl-1,4-benzenediol and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane = 1:1 (10 mL) solvent, followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the flux reached 3.5 F / mol. The product, 2,6-dimethyl-1,4-benzoquinone, was obtained by column chromatography. Yield: 66%.

[0095] Example 39:

[0096] In a single-chamber electrolytic cell, 144.6 mg (1.0 mmol) of 2-chlorohydroquinone and 32.4 mg (0.2 mmol) of ferric chloride were added to a water:dichloromethane solution of 1:1 (10 mL), followed by 42 μL of 37% concentrated hydrochloric acid. A graphite sheet electrode was used as the anode, and stainless steel as the cathode, at a current of 25 mA / cm². 2 Electrolysis was performed under constant current with stirring at 40°C. Electrolysis was stopped when the flux reached 3.5 F / mol. The product, 2-chlorohydroquinone, was obtained by column chromatography. Yield: 67%.

Claims

1. A method for the indirect electrolytic synthesis of p-benzoquinone, characterized in that, Includes the following steps: Step 1: Using hydroquinone as a raw material, in the presence of solvent and additives, and with iron salt as an electrocatalyst, at 0-40°C... o p-Benzoquinone was generated by constant current electrolysis of the electrode material under C conditions; the solvent was a mixture of dichloromethane and water; the additive was hydrochloric acid; and the current density was 10-50 mA / cm². 2 The reaction charge is 2 F / mol to 5 F / mol; the iron salt is ferrous sulfate, ferrous chloride, or ferric chloride; Step 2: The aqueous phase can be recycled. After electrolysis, simply add hydroquinone raw material and an equal volume of solvent, and then electrolyze again.

2. The method for synthesizing p-benzoquinone according to claim 1, characterized in that... The electrode material mentioned in step 1 is a graphite anode, or a graphite or stainless steel cathode.

3. The method for synthesizing p-benzoquinone according to claim 1, characterized in that: Temperature is 37-40 o C.

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