Enantioselectivity Study On Aldol Reaction Between Acetone And Benzene Carbonal Catalyzed By L-proline/γ-Al₂O₃

Based on HF and density functional theory(DFT) and B3LYP method, we made a theoretical study of the reaction system involving acetone and benzene carbonal catalyzed by L-proline andγ-Al2O3. Two models-chemical adsorption model and physical adsorption were adopted to study the reaction mechanism, We determined the structure of all eight transition states, and discussed the change of the structures in all four reactions. The single point energy and frequency of each structure was calculated. Four different reactions have been studied.The first reaction was between acetone and benzene carbonal catalyzed by L-proline. The purpose was to find two transition states and determined the main react ional mode. The calculated result shows that R configuration was primary, which was well agreed with the experimental result. When the reactants were put into alkalescency setting, the inversion of enantioselictivity was observed that the main product inversed into S configuration. When acetone and benzene carbonal was catalyzed by chemical adsorption model , S transition state was found to be more stable than R, so the dominating product will be S configuration. When the reaction was catalyzed by physical adsorption model, we found the R product would be primary.The calculated result shows that the O-H…O hydrogen bond between L-proline and benzene can induce the R product, while the hydrogen bond doesn't exist, the reaction result will be S product.