Correlation between the energy and electron density representations of reactivity: mPW1K study of the asymmetric SN2 reactions at the saturated nitrogen

Abstract

Abstract Gas phase inner-sphere electron transfer (ET) reactions of SN2, Y− + NH2X → X− + NH2Y (Y=H, CCH, CN, SH, OCH3, OH, NC, F, Cl, Br, and X=F, Cl, Br), have been investigated at the mPW1K/6-311++G(d,p) level. The correlation between energy (from potential energy surface) and electron density (from the theory of the atoms in molecules) representations of reactivity is presented. We conclude that the reactivity parameters of energy, electron density and geometry correlate well with one another within each group of Ys, which is gathered according to a similar electron density on the critical point of H–Y bonds. Moreover, within each group, Leffler–Hammond’s postulate is well confirmed. And the more looseness and the larger asymmetric of the TS, the lower the central barrier heights, hence the less electron density transferred is accomplished in going from the reactant to the TS. Also, in this type of ET reactions, ET takes place through the covalent bond.