MECHANISM OF THE REACTION OF CARBODIIMIDES WITH CARBOXYLIC-ACIDS

The kinetic parameters of the reaction of diphenylcarbodiimide with various carboxylic acids have been determined at a temperature interval of 20-160-degrees-C. The classical scheme for the reaction of carbodiimides with carboxylic acids is extended. It has been found that, at high temperatures, amides and isocyanates are the end products of the reactions. N-Acylureas, initially formed from aromatic carbodiimides and carboxylic acids, dissociate into isocyanates and amides at temperatures above 60-degrees-C. N-Acylureas formed by the reaction of carboxylic acids with aliphatic carbodiimides prove to be more stable: their dissociation temperature is about 50-degrees-C higher. Both the formation and dissociation of N-acylureas are much faster when the parent acid is stronger.