Synthesis of isocyanates
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Dear experienced friends, I am using p-chloroaniline along with triphosgene to synthesize p-chlorophenyl isocyanate, using toluene as the solvent and refluxing at 120 degrees. Does anyone know what catalyst can be added to accelerate the reaction and increase the yield? Also, what kind of developing agent would be suitable for monitoring the progress of the reaction using thin-layer chromatography? I’ve tried many things already… but it’s been very unsuccessful! :dizzy:
O-, m-, and p-chlorophenyl monoisocyanates can be synthesized using phosgene and o-, m-, and p-chloroaniline as starting materials, without the need for catalysts or initiators. Literature reports that 1,2-dichloroethane is used as the reaction solvent at reflux temperature ； The optimal reaction time for synthesizing o-chlorophenyl monoisocyanate is 5 hours, while the optimal reaction time for synthesizing m-chlorophenyl monoisocyanate and p-chlorophenyl monoisocyanate is 4.5 hours each ； The optimal molar ratio of o-chloroaniline to triphosgene is 2.2:1, while the optimal molar ratios of m-chloroaniline, p-chloroaniline to triphosgene are 2:1. Under the aforementioned reaction conditions, the yields of o-, m-, and p-chlorophenyl monoisocyanate were 85.6%, 87.2%, and 91.5%, respectively, with purities of 96.18%, 97.83%, and 99.55%, respectively. I hope this will be helpful for your production; it’s for reference only!
No catalyst is needed; petroleum ether and ethyl acetate are sufficient for separation, and no alcohols or amines should be added.