Theoretical Study On The Effect Of Substituent On The Nucleophilic Substitution Reaction Between N-(3-R-Pyridyl-2-yl)-methyl Aminosulfonyl And 2-iodin-acetamide

Density functional calculations were carried out to theoretical study of the SN2 reaction between N-(3-R-Pyridyl-2-yl)-methyl aminosulfonyl and 2-iodin- acetamide, discussing the effect of different substituent on the reaction barrier. The results indicate that:1. For the first pathway, thanks to the effect by the electronegativity of the R substituent,the effect of R substituent on the reaction barrier is carried out by the effect onσelectron of N(1). The impact of group of strong electronegativity on the reaction barrier is also big. If the R group and the molecule form the molecule inner hydrogen bond(The antibonding orbital of substituent H is regard as electron acceptor), the reaction barrier is diminished then;2. For the second pathway, the effect of substituent on the reaction barrier is carried out by the effect onπelectron of N(2).When R is strong donor group or strong electron withdrawing group respectively, the effect of substituent on the reaction barrier is superior;3. For the second pathway, the reaction barrier of withdrawing group R is greater than the reaction barrier of neutral group(H), the reaction barrier of neutral group(H) is greater than the reaction barrier of the donor group R;4. For the second pathway, if R group and molecular itself can?t form intramolecular strong hydrogen bond, then the stronger the power supplying of R group is, the smaller the reaction barrier is; if R group and molecular itself form intramolecular strong hydrogen bond, the reaction barrier demanded to form transition state increases.