Quantum Chemical Study On The Structure And Properties Of Superhalogen And Superacid Satisfying The Octet Rule

This paper mainly includes two parts:（1）Theoretical study of hetero-binuclear superhalogens and superacids based on the eight-electron rule;（2）The reaction mechanism of CO hydrogenation catalyzed by superacid based on the superhalogens structure of the eight-electron rule.The main content of the first part includes the theoretical calculation of the vertical electron detachment energy（VDE）value of the hetero-binuclear superhalogens and the gas-phase acidity of the superacids.The second part mainly includes the theoretical study of the stepwise and concerted mechanism in the CO hydrogenation reaction catalyzed by the superacids composite structures HMgX₃ and HMg₂X₅（X=F,Cl,Br）.The first chapter briefly describes the research background and significance of superhalogens and superacids,introduces the electron counting rules and main characteristics of superhalogens,as well as the application of new superacids in the field of catalysis are also introduced.Chapter2 briefly introduces the calculation methods and transition state theory involved in this article used in this thesis.In the third chapter,we systematically explore the basic properties of hetero-binuclear superhalogens and superacids designed based on the octet rule.The central atom is a combination of atoms from different main groups.The calculation results show that the VDE of all structures is greater than 3.6 e V,which is satisfy the definition of superhalogens.Secondly,through the analysis of the VDE value of the superhalogens,the law of the VDE of the hetero-binuclear superhalogens with the central atom and the number of bridges is obtained.Then,we tried to approximate the potential energy of the extra electron in the superhalogens by using the classical Coulomb effect,and studied its change law and compared it with the change law of the superhalogens’VDE.It is found that the potential energy of extra electron is an important factor affecting superhalogens’VDE.At last,this chapter uses superhalogens as the building block to design superacids and calculate their gas phase acidity.Under gas phase conditions,theΔG_acid values of all composite structures are all less than 300 kcal/mol,which meets the theoretical requirements of gas phase superacids.Further analysis shows that the acidic change trend of the composite structure is mainly related to the increase of the superhalogens’VDE value.In most cases,the higher the VDE value of the superhalogen part,the stronger the acidity of the composite structure.In the last Chapter,we systematically studied the mechanism of the stepwise and concerted reaction hydrogenation of CO catalyzed by HMgX₃ and HMg₂X₅（X=F、Cl、Br）.The results show that for the CO hydrogenation reaction,all the acid catalysts designed in this chapter can lower the reaction energy barrier compared with direct reactions and hydrogen halogens catalyzed reactions.The superacid constructed from superhalogen as the building block has better catalytic efficiency.In most cases,the energy barrier of the concerted reaction is lower than the rate determining step of the stepwise reaction.Therefore,it is more likely that the reaction will proceed in a concerted mechanism.Then through comparative analysis of different factors that may affect the reaction energy barrier,we found that the stronger the acidic composite structure,the lower the reaction energy barrier.In the last,we calculate the reaction rate constant to provide a more intuitive way to express the efficiency of the catalyst designed in this chapter to catalyze the reaction.The reaction rate constant can be corrected by the transmission coefficient,and a more accurate reaction rate constant can be obtained.It can be concluded that superacid constructed from superhalogen as building block have better catalytic efficiency.