AB-INITIO ANALYSIS OF WATER-ASSISTED REACTION-MECHANISMS IN AMIDE HYDROLYSIS

The water-assisted hydrolysis of formamide has been studied at the MP3 /6-31G*//3-21G ab initio level for neutral and H3O+-promoted processe s. The computations predict an important catalytic effect through O-pr otonation, in agreement with previous results for the nonassisted reac tion. Assistance by a water molecule lowers the free energy barriers o f the neutral and the acid-promoted reactions, but the effect is espec ially large in the second case. The influence of electrostatic interac tions with the bulk is discussed using a continuum model to represent the liquid. Substantial modifications of the transition-state geometri es are predicted, but the average change in the activation barriers is rather small.