Quantum Chemistry Study Of XNO₂(X=Cl, Br, I) Isomers And Isomerization Reaction

XNO₂(X=F,Cl,Br,I)are widely existed in the stratosphere,troposphere and the marine boundary layer.Those compounds are getting more and more attentions of people because of their roles in the ozone depletion process.Besides that,the reactions of XNO₂ with the other molecules are very easy to occur,which makes the study of these reactions become very significant.In this thesis,ClNO₂,BrNO₂,INO₂ isomers and isomerization reactions were studied using quantum chemistry method and the topological analysis of electronic density.The results will provide useful information on the isomerzation reaction and offer a theoretical basis for eliminating certain pollution molecules in the atmosphere.In chapter one,a brief description of the roles that XNO₂(X=F,Cl_Br,I)are played in the atmosphere is given,we have also reviewed the recent study on XNO₂ at home and abroad.At the second part of the work,the wide application of Quantum Chemistry and Quantum Chemical Topology was summarized.The main studies consist of four parts,the first three parts show the structures of XNO₂(X=F,Cl,Br,I)isomers and isomerization reaction mechanisms of them.We found eight possible isomers each of XNO₂(X=F,Cl,Br,I)and classified those isomers by their different structures.The mechanisms of the isomerization reactions between the same type of isomers and the different types of the isomers are discussed in detail using topological analysis of electronic density.The rule of chemical bond in the reactions is also discussed with topological analysis of electronic density.In chapter six,the structures and the related reaction properties of all the different isomers of XNO₂(X=F,Cl,Br,I)are summarized and compared.The results show that:the order of the stability of the two similar configuration isomers from all the isomers we have found is that:cis-isomer is more stable than trans-isomer. For the isomers which have different configurations,the order of their stability is: XONO-cis and XONO-trans,XOON-cis and XOON-trans,XNOO-cis and XNOO-trans.The isomerization energy barriers of XNO₂(X=F,Cl,Br,I)are in the order of:FNO₂,ClNO₂,BrNO₂.The result shows that,the isomerizations of BrNO₂ are most likely to occur.The isomerization mechanisms of XNO₂(X=F,Cl,Br,I)can be summarized as follows:For the two similar configuration isomers,it is included bond rotation or the variation of bond angle.For the isomers with different configurations,the recombination of the molecular framework combine with bond rotation or the change of bond angle,atom migration is included.The novel conclusions and ideas of this work are listed as follows:1.Five new isomers of XNO₂(X=F,Cl,Br,I)were found by the theoretical calculation,they are XNO₂-p,XNOO-cis,XNOO-trans,XOON-cis,XOON-trans, respectively.2.the isomerization process of the eight different isomers of XNO₂(X=F,Cl,Br,I)were studied by the topological analysis of electronic density.We have also discussed the thermodynamics and kinetics stability of those isomers,predicting the possibility of their existence.3.classification have carried on the summarization mechanisms of XNO₂ (X=F,Cl,Br,I),the isomerization can be achieved in these ways:For the two similar configuration isomers,it is included bond rotation or the variation of bond angle.For the isomers with different configurations,the recombination of the molecular framework combine with bond rotation or the change of bond angle,atom migration is included.The order of the XNO₂(X=F,Cl,Br)energy barrier is FNO₂,ClNO₂, BrNO₂.4.The analysis for the typical reactions of the isomerization of XNO₂(X=F,Cl,Br,I)by the topological analysis of electronic density indicates:Some reactions experienced three-member ring transition region and structure transition state,while some reactions experienced four-member ring transition region and structure transition state.Not only planar structure but also non-planar structure was found in the four-member ring transition structure.