1,2,4-Trifluorobenzene

1,2,4-Trifluorobenzene

C₆H₃F₃

CAS No.:367-23-7

Preparation：

step 1.

Making 2,4-diaminofluorobenzene: Fill a high-pressure reaction kettle with 50.0g of 2,4-dinitrofluorobenzene, 500.0g of ethanol, and 1.0g of Raney nickel catalyst. First, nitrogen is added to the sealed high-pressure reaction kettle. Replace the reactor's air three times with hydrogen, charge it with hydrogen until the pressure reaches 2.0 MPa, and then raise the temperature to 70°C. Keep the closed high-pressure reactor's pressure at 2.0 MPa and react for 2.5 hours at 90°C. Filter the Raney nickel catalyst once the reaction is finished. After rectification and atmospheric distillation of the resulting filtrate, a batch of light yellow oil is produced. 31.6g of 2,4-diaminofluorobenzene had a GC purity of 99.2% and a yield of 93.2%.

Step 2.

Fluoroboric acid diazonium salt preparation: To a four-necked flask, add 252.0g (2 mol) of the 2,4-diaminofluorobenzene that was generated in step one. Step one can be carried out sequentially or simultaneously to collect 252.0g in order to reach this amount. Follow the instructions until 252.0g of 2,4-diaminofluorobenzene is collected (you can alternatively use more ingredients in proportion to the amount of 2,4-diaminofluorobenzene that is obtained). Once the mixture is at room temperature, add Put 1320g of a 40% concentrated fluoroboric acid aqueous solution (6 mol of fluoroboric acid) into a four-necked flask.Following the dropwise addition, rapidly lower the reaction system's temperature by adding ice brine and an aqueous solution of fluoroboric acid at a mass concentration of 20–30%. To obtain 570g of fluoboric acid diazonium salt intermediate, which has an 88% yield, add 365g of sodium nitrite aqueous solution (a solution consisting of 145g (i.e., 2.1mol) sodium nitrite and 220g water) dropwise while maintaining the temperature at -25 to 0°C.

Step 3.

1,2,4-trifluorobenzene preparation: Assemble a reflux condenser tube in a 1000 ml four-neck flask. A second four-neck flask with a standard capacity of 1000 milliliters is connected to the condenser tube by an air guide tube. Fill the four-necked flask with 585.0g of the fluoroboric acid diazonium salt intermediate that was generated in step 2. You can either operate step 2 sequentially until 585.0g of fluoroboric acid is collected, or you can conduct step 2 simultaneously to collect 585.0g. intermediates of diazonium salts;You can also increase the amount of ingredients used in proportion to increase the amount of fluoroboric acid diazonium salt intermediate), and add 400g of ether to the second four-necked flask, and heat the four-necked flask to 120°C within 1 hour. , keep it warm for 2 hours, then raise the temperature to 180°C within 1 hour, keep it warm for 2 hours, and decompose the boron trifluoride gas produced The ether that enters the second four-necked flask through the air conduit is absorbed by the ether, and 600g of boron trifluoride ethereal solution with a mass fraction of 40% is obtained. At the same time, the residue decomposed in the four-necked flask is distilled under normal pressure to obtain the mass It was 195g of 1,2,4-trifluorobenzene, the GC purity was 99.2%, and the yield was 82%.

Packing, Storage, Handling and Transportation

Hexafluorobenzene should be sealed in dry place at room temperature.

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