Synthesis
In a 1000 ml four-necked flask, 926.97 g of 98% concentrated sulfuric acid was added with stirring and the temperature was maintained at 10 to 15°C. 200.72 g of 97.7% nitric acid was added slowly and dropwise. After the nitric acid was added, 300.0 g of dimethyl terephthalate was added and the reaction temperature was maintained at 10 to 15°C for about 30 minutes. Subsequently, the reaction temperature was controlled at 15 to 20°C and the reaction was continued for 30 minutes before the endpoint of the reaction was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the reaction mixture was stirred for 15 minutes, filtered, and the filter cake was sequentially washed to neutrality with 900 mL of 5% aqueous sodium hydroxide and 500 mL of water. The filter cake was suspended in 3000 ml of water and stirred for 30 min at room temperature. Next, the mixture is transferred to a recrystallization unit and 1500 g of ethanol is added for recrystallization: the solid is first heated to 50 to 55°C to dissolve completely, then slowly cooled to below 5°C to promote full precipitation of the product. The precipitate was collected by filtration and dried to give 382.5 g of crude product. Further vacuum drying at 60°C gave 351.2 g of the white crystalline product, dimethyl 2-nitroterephthalate, in 95% yield (as dimethyl terephthalate). The product was analyzed by gas chromatography and showed a purity of greater than 99% with a melting point of 73.8 to 75.5°C (literature value: 73 to 76°C).
References
[1] Journal of Organic Chemistry, 2001, vol. 66, # 12, p. 4356 - 4360
[2] Patent: CN103524386, 2016, B. Location in patent: Paragraph 0029; 0030; 0031
[3] Patent: CN104072403, 2016, B. Location in patent: Paragraph 0031-0033
[4] Liebigs Annalen der Chemie, 1987, p. 833 - 838
[5] Justus Liebigs Annalen der Chemie, 1912, vol. 393, p. 25
