Abstract: Using the dispersion correction density functional WB97XD method, the MP2 method of perturbation theory and the SMD model method of selfconsistent reaction field, we studied the chiral enantiomer transition of two aspartic acid (Asp) molecule in dominant reaction channels, the catalysis and the solvent effect of water molecules.  The results show that the chiral enantiomer transition is realized by a series of Asp transition states of the rotation of αcarboxyhydroxyl, βcarboxyhydroxyl,  βcarboxyl and Rgroup and proton transport from αcarbon to amino nitrogen, from amino nitrogen to αcarbon and in carboxyl groups, and several kinds of optical isomerism products with different configurations are obtained. The intrinsic energy barriers of Asp molecules with two strong single hydrogen bonds and two moderate strength single hydrogen bonds in the dominant channel are 2585, 2538 kJ/mol, respectively, which are derived from the transition states of transfer of αhydrogen to aminonitrogen, and that are reduced to 133.3, 134.3 kJ/mol by the catalysis of two water clusters, and to 106.3,  107.8 kJ/mol in water solvent environment, respectively. 
Therefore, the chiral enantiomer transition of Asp molecules can be realized slowly by the catalysis of water molecular clusters, and the reaction rate can be accelerated by the water solvent effect.

Key words: chiral enantiomer, aspartic acid, density functional theory, perturbation theory, SMD model, transition state, solvent effect