METHOD FOR INCREASING THE 4,4' DICARBAMATE ISOMER OF THE DIPHENLMETHANE DICARBAMATES DURING PREPARATION THEREOF

摘要

A METHOD FOR INCREASING THE 4,4' DICARBAMATE ISOMER OF THE DIPHENYLMETHANE DICARBAMATES DURING PREPARATION THEREOF A method for increasing the 4,4' disubstituted isomer of the diphenylmethane dicarbamates produced by the acid catalyzed condensation of an N-aryl carbamic acid ester, such as ethylphenylcarbamate, with a carbonyl compound, such as formaldehyde, which comprises carrying out the condensation in a single phase system with a dilute solution of the N-aryl carbamic acid ester in an inert solvent having a dielectric constant of atleast 20 at 20.degree.C. The solvent must have good solubility for the carbamates, which carbamates are employed in the solvent at concentrations of from about 0.1 to 50 weight per cent to provide a product enriched with the 4,4'-diphenylmethane dicarbamate isomer.