Based on anmino used as hydrogen transfer bridges

chiral transition mechanism of α-alanine molecule was studied under the water environment through the B3LYP methods of density functional theory and the MP2 methods of perturbation theory as well as the smd models of SCRF. The result of structural analysis suggested that the bond angles 1C-13H-14O and 18O-15H-6N between transition state aTS2·2H

2

O of seven membered ring and aTS2·3H

2

O of nine membered ring were significantly larger than that 1C-13H-14O and 14O-15H-6N of transition state aTS2·1H

2

O of five membered ring. There were two channels in the chiral transition reaction

in which one the hydrogen of chiral carbon used the imino N as a bridge and was transferred to the other side to achieve chiral transition

the other that was firstly transferred to carbonyl and then to the other side using amino as a bridge. Calculations of potential energy surface showed that the first channel was the dominant reaction channel

where the process of the hydrogen from chiral carbon to amino was the rate determining step and the energy barrier is reduced to 122.5 kJ·mol

-1

when using three water molecules as transfer media. The water molecules had good catalytic effect on the proton transfer in α-Ala molecule

and the solvent effect on water made the energy barrier of the non proton transfer reaction increase slightly.