Theoretical Study On The Properties Of Furan,pyrrole And Their Derivatives In Terms Of Molecular Face Theory And Fukui Function

Molecular face can be used to describe not only the molecular contour,shape and size,but also distribution electron density and Fukui function.In this thesis,in terms of MF theory,we can calculate and study the first ionization energies,bond lengths of the chemical bonds concerned,the absolute value of single electron potentials in the ring center(D_pr)and at the bond center(D_pb)for the furan,pyrrole and 44 their derivatives.We explore the effect of different substituents on the properties of these derivatives and predict the electrophilic reaction sites of these derivatives.The detailed contents are as follow:MP2/6-311++G（3df,3pd）level of theory is used to optimize the structure of furan,pyrrole and 44 their derivates,then stable structures and the bonds lengths of the chemical bond of these compounds are obtained.MP2/6-31G method is employed to calculate the first ionization energy of these compounds.The absolute value of single electron potential at the ring center(D_pr)is obtained by using CISD/6-31G in MELD package in combination with our own program.We discuss the effects of different substituents on the properties of these derivatives about the first ionization energy,bond length as well as D_pr,respectively.The electrophilic reaction possible sites of the five-numbered heterocyclic derivatives are predicted on the basis of molecular face theory.Single electron potential barrier of chemical bond(D_pb)in furan,pyrrole and 44 derivatives can be obtained by using CISD/6-31G method.Molecular intrinsic characteristic parameters of these compounds are calculated by using the same method.For the derivatives displacing H2 atom,the order of D_pbs of C-H chemical bonds is C5-H5>C3-H3>C4-H4.Whereas for the derivatives displacing H3 atom,the order of D_pbs of C-H chemical bonds is C2-H2>C5-H5>C4-H4.The D_pb of C4-H4 chemical bond has minimum.Therefore,the chemical bond is the weakest and easily breaks.It can be obtained that the position of C4 atom is the site of electrophilic reaction.f^-（r）is an index of predicting the electrophilic reaction sites.f^-（r）distribution mapped on MF may be used to judge the sites of electrophilic reaction.CISD/6-31G method is used to calculate the f^-（r）value along the direction perpendicular to the plane of five-membered ring.For each derivative displacing H2 atom,the f^-（r）value of C5 atomic region has much bigger,thus the reactivity site is placed in the above C5 atom.For every derivative displacing H3atom,the f^-（r）values of C2 and C5 atomic region have much larger,so they are the reactive sites.In the thesis,MF theory is applied to calculate and discuss the properties of furan,pyrrole and their derivatives.It provides us a theoretical reference for further researches which include the effect of different substituents and predication of electrophilic reaction sites.