2,6-dichloro-4-trifluoromethylaniline is an important intermediate of medicine and
Pesticide, such as regent, cyfluthrin, flumuron and so on. In addition, its heavy ammonia salt can condense with itself or with other compounds to form many useful dyes, insecticides and herbicides. There are usually two methods to prepare 2,6-dichloro-4-trifluoromethylaniline: ammonolysis proposed by seiwell in 1979, and a new process proposed by danc (21 w) olfgang in 1995. Most of 2,6-dichloro-4-trifluoromethylaniline in China is still under laboratory development and improvement. Because aniline products have great toxic and side effects, environmental protection and labor protection are particularly important in the production of this product. 1 experimental part 1.1 experimental materials 4-trifluoromethylaniline (99.0%), liquid ammonia (99.9%), cuprous chloride (98.0%), potassium fluoride (99.0%), anhydrous hydrogen fluoride (99.9%), 4-trichloromethylbenzene isocyanate (95.0%). 1.2.14 synthesis of trifluoromethylaniline in a 100ml stainless steel autoclave, 6.00g 4-chlorotrifluoromethylbenzene, 0.62g cuprous chloride, 387g potassium fluoride, 1625g ammonia, 2240g methanol and 0.24g undecane were successively added. After heating to 200 ℃ for 5 hours, cool and vent ammonia. 68 g of 4-trifluoromethylaniline was obtained by vacuum distillation. 1.2.2.6 synthesis of dichloro-4-trifluoromethylaniline put 500 g of 4-trifluoromethylaniline into a 500 ml reaction flask and added 100 ml glacial acetic acid. Start stirring and raise the temperature to 60 "C. Pass through chlorine gas until the trace material of GC is less than or equal to 0.5%. After cooling, filtration and water washing, a light yellow solid of 26-dichloro-4-trifluoromethylaniline was obtained, which was 68.5g and 98% in content. HNMR data: D = 7.262 (s.2h, two hydrogens on benzene ring). The results of three batches of tests were: 68.5g (including 98.0% and 94.0%); 68.3g (including 98.3% and 94.0%); 69.og (including 98.0% and 94.7%). 1.3 Wolfgang's isocyanate synthesis 1.3.14 synthesis of trifluoromethylaniline 1L stainless steel pressure kettle, equipped with electromagnetic stirring and reflux condenser. A vent valve is arranged on the upper part of the condenser. Dry and replace the whole system with nitrogen. 118 g of 4-trichloromethylbenzene isocyanate and 300 g of anhydrous hydrogen fluoride (water content ≤ 0.1%) were added to the autoclave in turn. Close the autoclave, start stirring, heat the reactant to 70 ℃ and keep it for 4 hours. During the reaction, the vent valve on the upper part of the condenser should be opened frequently to make the pressure of the reaction system less than 1MPa. After the reaction, cool the material to (30-35) ℃ and vent to collect excess hydrogen fluoride. Pour the material into 250 ml ethyl acetate to dissolve. Then transfer to 250ml ice water, stir vigorously, adjust pH = 8-10 with 30% potassium hydroxide. Separate the upper oil layer, wash it with water and saturated sodium chloride solution once, and dry it with anhydrous magnesium sulfate. 675g 4-trifluoromethylaniline (86 ℃ / 14mmHg) was obtained by vacuum distillation. The results of three batches of tests were: 67.5g (including 99.0% and 87.5%); 67.8g (including 98.9% and 87.8%); 67.5g (including 98.8% and 87.4%). 1.3.2 the synthesis of 2,6-dichloro-4-trifluoromethylaniline is the same as that of 12.2. 2 discussion and conclusion the process of synthesizing 4-trifluoromethylaniline by ammonolysis is simple, but the reaction condition is harsh, which needs to be carried out under high temperature and high pressure, and the conversion rate is low. Synthesis of 4-trifluoromethylaniline by isocyanate method is a new method developed in recent years. Abroad, Hester company, Rhone Planck company and occidental company are all studying. 4-trichloromethylbenzene isocyanate can be prepared by the reaction of 4-trichloromethylaniline with phosgene. In the preparation of 4-trifluoromethylaniline, it must be noted that the product can not be distilled at 200 ℃ under normal pressure, otherwise, violent polymerization will occur, releasing a large amount of hydrogen fluoride and forming glassy resin.
