Study On Generalized Anomeric Effect And Molecular Acidity And Basicity By Information-Theoretic Approach

Density functional reactivity theory?DFRT?is an extension of density functional theory?DFT?,which can describe molecular properties better from the point of view of electron density.Prior to this,we have successfully applied density functional theory to the characterization of S_N2 reactions,electrophilic nucleophilic reactions,aromaticity and other molecular property,and its research results are reliable and accurate.In this paper,we selected two kinds of molecular chemical properties:terminal isomerization effect and molecular acidity in molecular chemical activity,and studied them by using information theory and energy decomposition analysis in density functional theory,and obtained better theoretical characterization methods and means.In the study of end-group isomerization effect,we selected 45 systems with general formula of R₁-X-CH₂-Y-R₂,in which R₁ and R₂ are functional groups and X and Y are heteroatoms with electronegativity.End-group isomerization is one of the three-dimensional effects of electrons.We studied the energy difference between the two isomers and the information theory method in density functional theory of activity.Our results show that,in most cases,the end group isomerization effect is effective for the stability of molecules.The main reason for the end group isomerization effect is the electrostatic interaction?Ee?of electrons,but the space potential resistance energy?Es?and hyperconjugation??-??of electrons also play an indispensable role.In this study,the information theory method can well describe the end-group isomerization effect and get good results.We also compared and discussed the relationship between the end group isomerization effect and the traditional comonomer effect?i.e.in copolymerization reaction,the influence of the involvement of comonomers on the polymerization behavior and the structure of polymers?.The end group isomerization effect mainly increases the stability of molecules,and the comonomer effect mainly affects the structure of polymers,thus increasing the stability of polymers.Qualitative.Molecular acidity is one of the important physical and chemical properties of molecules,but its accurate calculation and prediction are still unsolved problems in theory.In this paper,the information theory approach?ITA?in density functional activity theory is used to quantitatively describe molecular acidity from a new perspective.Firstly,we selected five different types of oxyacid series to study,namely monosubstituted and disubstituted benzoic acid,monosubstituted benzenesulfonic acid,phenylselenite,phenols and alkyl carboxylic acid.In addition,we also carried out similar studies on nitrogen-containing systems,including primary amine,secondary amine and tertiary amine.For oxygen-containing systems,we compared the information physical quantities such as Shannon entropy,Fisher information entropy,GBP entropy,information gain,Onicescu information energy and relative Rényi entropy of acidic atoms?oxygen atoms?in neutral molecules with experimental pK_a values,and the fitting results predicted the molecular acidityandalkalinityofoxygen-containingsystems.For nitrogen-containing systems,we have selected various kinds of nitrogen-containing molecules,including amino acids,pyridine,aniline and simple primary secondary tertiary amines,to do similar studies by means of oxygen-containing systems.However,our results are not satisfactory.This may be related to the complexity of choosing nitrogen-containing molecules,which leads to a linear relationship between the pK_a values fitted by information content and the experimental pK_a values.It's not ideal.Through the systematic study of end-group isomerization effect and pK_a value of oxygen-nitrogen system in this paper,we are more confident about the application of information theory in the prediction of chemical activity in density functional theory.It is expected that the results of end group isomerization can be extended to other phenomena with space electron effects,such as the?-gauche effect.For the study of pK_a in nitrogen-containing systems,we need to refine the calculation and statistical process,find more valuable information,and extend the study of pK_a value to other fields,such as acid prediction of superacid.This paper expands the application scope of information theory method in density functional activity theory,and makes a contribution to the improvement of density functional activity theory.