The title reaction was researched in the theory by ONIOM method conbined with quantum mechanics and molecular mechanics

and the SMD model method based on self consistent reaction field (SCRF) theory. The study showed that there were two channels a

b in the title reaction. In channel a the hydroxyl radical water molecule cluster acted with

α

-H and amino nitrogen through hydrogen bond to form substrate

and in channel b that acted with

α

-H and carbonyl oxygen through hydrogen bond to form substrate. Calculations of potential energy surface showed that with hydroxyl radical and water clusters as the proton transfer media

optical isomerism of α-Ala was induced by water molecules pulling

α

-H

and in water vapor environment

channel a was the dominant one and the energy barrier of the rate-determining step was 136.1 kJ/mol

but in water liquid environment

the dominant channel was b

the intrinsic barrier of transition state was 78.1 kJ/mol. The dominant channel where

α-

Ala  damage induced by the

α

-H abstraction of hydroxyl radical assisted with water molecule cluster was a

the energy barrier of the rate-determining step was 25.3 kJ/mol

which was reduced to 22.1 kJ/mol by water solvent effect. The results showed that hydroxyl radical can make optical isomerism and the damage of

α-

Ala occurs simultaneously in water liquid phase environment

and the damage had obvious advantage in competition. The confinement effect of MOR zeolite changed optical isomerism mechanism of

α-

Ala and played a better role in catalysis.