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Following pyrolysis the residual material in the flask had a composition of 25 mole percent phenyl N-methylcarbamate and 75 mole percent phenol. The flask was cooled, a vacuum applied and phenol was stripped at a pressure of 20 mm Hg. Recovered phenol was also chromatographically pure. The residual carbamate remaining after phenol was stripped was returned to the pyrolysis flask. After 3 cycles of pyrolysis and phenol stripping, analysis showed: 96% conversion to methyl isocyanate, 2% unconverted material and 2% conversion to the allophanate. The methyl isocyanate was identified by reaction with aniline to give 1-methyl-3-phenylurea melting at 149°-150.5° C.

1. temperatureThe flask was cooled