Theoretical Study On The Catalytic Effect Of ?-cyclodextrin In Reaction

The density functional theory(DFT)method is used to study ?-cyclodextin(?-CD)in organic reactions as catalyst.(1)DFT study on the effects of ?-cyclodextrin in synthesis of 2-phenylbenzimidazole via benzaldehyde and o-phenylenediamine;(2)DFT study on the effects of catalysis by ?-cyclodextrin in the reaction of p-nitrophenyl acetate;(3)DFT study the interaction of ?-cyclodextrin with2-bromo-1-phenylethanone and benzothioamide.The conversion of o-phenylenediamine and benzaldehyde to2-phenylbenzimidazole can be improved overtly under ?-cyclodextrin(?-CD).density functional theory(DFT)method is mainly used throughout the study.According to the energy(the binding energy,the deformation energy)and structural deformation,entry models and reaction process can be pinpointed,viz o-phenylenediamine embed ?-CD from wide rim,then benzaldehyde pass into the inclusion from the narrow rim.Then natural bonding orbital(NBO),Mulliken charge,frontier orbital,Fukui function and nuclear magnetic resonance(NMR)are employed to reveal the mechanism of reaction.Mechanism illustrates that ?-CD plays a catalytic role in the synthesis reaction on secondary side,improving the reactivity and selectivity of the process.The reaction of p-nitrophenyl acetate and ?-alanine can be improved apparently with ?-cyclodextrin(?-CD)according to previous researches,the interaction mechanism between ?-cyclodextrin and p-nitrophenyl acetate is described in this paper.Density functional theory(DFT)method is employed throughout the study.According to the energy(the binding energy,the deformation energy)and structural deformation,entry models and reaction process can be pinpointed,viz p-nitrophenyl acetate embed ?-CD from the wide rim.Then frontier molecular orbital,dual descriptor,natural bonding orbital(NBO),and nuclear magnetic resonance(NMR)are used to reveal the mechanism of reaction.The mechanism illustrates that ?-CD plays a catalytic role during the synthesis reaction,improving the reactivity and selectivity of the process.The experimental results showed that the reaction rate and yield of2-bromo-1-phenylethanone and benzothioamide were significantly improved under the control of ?-cyclodextrin,and the possibility of inclusion of two guests and ?-CD was studied,and the property.By studying the inclusion of 2-bromo-1-phenylethanone,benzothioamide and ?-CD,the most stable configuration of the two inclusions can be found,followed by HOMO-LUMO,Mulliken charges,and NMR used to analyze the mutual change after inclusion.The calculated data indicate that the chemical environment of both host-guest inclusion complexes changed,that is,after inclusion,?-CD and the guest undergo chemical changes and change the charge density of the major groups,which indirectly confirms the rationality of the experimental data,while roughly presuming the possible mechanism of the reaction.