Synthesis of 4-nitroimidazole has been discussed in this paper.The neutral reaction of imidazole with concentrated sulfuric acid produces disulfuric imidazole salt

which can then be converted to 4-nitroimidazole by nitration reaction with mixed acids of sulfuric acid and nitric acid.An optimal production condition has been obtained by the orthogonal experiment: molar ratio of imidazole and nitric acid is 1∶1.2

volume ratio of oleum sulfuric acid(10%) and nitric acid is 3.4∶1

reaction temperature(55~65) ℃

reaction time 2 h

yield 92.7%.The nitration selection and thermal stability of 4-nitroimidazole have also been discussed.