Process for the preparation of N-monosubstituted carbamic acid esters

A process for the preparation of an N-monosubstituted carbamic acid ester which comprises reacting an unsubstituted carbamic acid ester having the formula NH.sub.2 CO.sub.2 R wherein R is a straight or branched chain alkyl group containing from 1 to 10 carbon atoms, with an aromatic primary amine having the formula R'(NH.sub.2)n wherein R' is a substituted or unsubstituted aryl or aralkyl group containing one or more benzenoid rings which may be fused or joined by single valency bonds and n is an integer of 1 to 6, at a temperature in the range of from about 125.degree. C. to 250.degree. C. in the presence of a monohydric aliphatic alcohol having from 1 to 10 carbon atoms and a catalytic amount of from about 0.01 to 30 mole percent based on the aromatic primary amine employed of a tertiary amine which may be an aliphatic, cycloaliphatic, aryliphatic or aromatic amine containing from 1 to 18 carbon atoms.