Regularities of 2-methylimidazole synthesis and technology of its production

He regularities of 2-methylimidazole synthesis are represented in the article. The basic reaction for 2-methylimidazole synthesis is condensation of glyoxal, acetaldehyde and ammonia. The process is carried out in four stages: first of all the acetaldehyde reacts with ammonia at 0-5°C and further intermediate condenses with glyoxal. Then reaction mixture is evaporated and distillated. The study of the process was carried out by means of the laboratory reactor, the products were identified with IR-spectroscopy, NMR-spectroscopy, differential scanning calorimetry and gas chromatography. It has shown that the intermediate and glyoxal should be mixed at maximum 70°С and further condensation should be carried out at maximum 95°C. The main product evolving conditions for vacuum evaporation and distillation were optimized. Vacuum evaporation (i.e. reaction mixture concentration) should be carried out at 65-75°C and 1,5-2 kPa. Finally reaction mixture should be dried at 110 C and main product distillation should be at 160°C. In addition, the time of synthesis was determined and it has shown that condensation should be carried out for at least 3 hours to achieve the declared yield of 2-methylimidazole. The lowering of synthesis duration leads to sharp decreasing of 2-methylimidazole yield, longer synthesis does not lead to 2-methylimidazole yield changes. The optimal molar ratio of reagents was determined. 2-methylimidazole synthesis is necessary to be carried out with molar ratio applicable to reaction stoichiometry, i.e. glyoxal : acetaldehyde : ammonia = 1 : 1 : 2.

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