Abstract: This paper is one of a series of reports of theoretical researches on the mechanism of the Mannich reaction using the iminium salt as the potential Mannich reagent. According to the results of AM1 dynamic calculations, the activation energies of key steps in conventional Mannich reactions between ammonia, formaldehyde and acetaldehyde in neutral and acidic media are 438.8 kJ/mol and 393.9 kJ/mol respectively. The activation energy of the rate-controlling step of the Mannich reaction which contains the potential Mannich reagent is 274.7 kJ/mol. Therefore, it can be derived that the potential Mannich reagent can increase the rate of the reaction remarkably. The reasons for this have been discussed in terms of the orbital match and electrostatic interaction between the atoms of reactant complexes. In this paper another different conjectured mechanism of the potential Mannich reagent which can reduce the activation energy is considerably studied.

Key words: Potential Mannich reagent, Mannich reaction, AM1 method, Activation energy