Phosgene → N,N-Diphenylcarbamic chloride

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Reaction Steps

By way of illustration, one mole of diphenylamine is reacted with a 10% molar excess of phosgene in a suitable solvent such as monochlorobenzene, to yield diphenylcarbamyl chloride. The carbamyl chloride thus produced is reacted further with n-propyl amine in stoichiometric amounts, in the presence of a mole of caustic soda. Diphenyl propyl urea (DPPU) is formed in essentially stoichiometric amounts. The DPPU formed may be either separated from the solvent or, if desired, supplied as a solution in its reaction solvent. DPPU pyrolyzes at 210°-220° C. to yield n-propyl isocyanate of 99% purity and greater than 90% yield. The diphenylamine remaining may be returned easily in tankcars or tankwagons for reprocessing.

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