SUBSTITUENT EFFECT IN REACTION OF DICYCLOHEXYLCARBODIIMIDE WITH SUBSTITUTED BENZOIC-ACIDS

A curved Hammett relationship was observed for the reaction of substit uted benzoic acids with dicyclohexylcarbodiimide in buffered solution. The reaction is promoted by electon-withdrawing substituents because of larger concentration of the acid anion present in the reaction mixt ure. On the other hand, electron-donating substituents encourage nucle ophilic attack of the acid anion on the protonated carbodiimide.