Study On Synthesis Of Phenyl Carbamates And Isocyanates Using Carbamate Anion Method Under Mild Temperature And Pressure

In this paper, the carbon dioxide together with the primary amines were used as raw material to generate the carbamates and isocyanates. The generating reaction was occurred under the room temperature and pressure while using organic base as catalyst and acetonitrile as the solvent. In process of the reaction, the carbon dioxide played a role of a carbonylation agent to carbonylate the aniline to carbamate anion which is strong nucleophiles. And the carbamate anion was reacted with chlorinated hydrocarbons and electrophilic dehydrating agent to generate carbamate and isocyanates. Through orthogonal and single factor experiments with qualitative and quantitative analysis by using FT-IR spectrometer and GC/MS instrument, the influences on yields of various reaction conditions were analyzed and discussed with the guide of reaction thermodynamics analysis to find an optimalizing results and a optimal operation condition.It was found that in the generating process of carbamate anion, the use of strong basic nitrogen could promote the positive reaction of carbamate anion generation, and make a better yield under the room temperature and pressure condition. And the use of higher steric hindrance and higher alkaline organic base would also lead to a better yield. The best conditions of synthesis of phenyl carbamates were:1-Bromobutane/aniline molar ratio:4:1, the organic base/aniline molar ratio:1:1, reaction temperature 70℃,3 hours of reaction time, and the highest Butyl-phenyl-carbamate yield is 63.2%. The best conditions of synthesis of phenyl carbamates were:dehydrating agent/aniline molar ratio:2:1, the organic base/aniline molar ratio:3:1, reaction temperature-5℃,60minute of reaction time, the highest yield of phenyl-isocyanates is 7.5%.The carbamate anion method that uses carbon dioxide as raw material to generate carbamate and isocyanates can not only save the cost of raw materials, but also contribute to the safety and the decreasing of greenhouse gas emission by using the CO2 instead of highly toxic phosgene, thus reduces the negative impact on the environment, and it will has a good economic and environment effect.