A comprehensive theoretical study on the identity ion pair SN2 reactions of LiX with NH2X (X=F, Cl, Br and I), structure, mechanism and potential energy surface

Gas phase identity ion pair SN2 reactions at nitrogen LiX + NH2X → XNH2 + LiX (X=F, Cl, Br and I) are investigated at the G2M(+) level. Two reaction mechanisms, inversion and retention, are proposed. Results indicate the inversion mechanism is favorable for all halogens. Including Li in the anionic SN2 model will raise the overall barriers for the LiX + NH2X (X=F, Cl and Br) reactions and lower the overall barrier for the LiI + NH2I reaction. The stabilization energies for complexes XLi⋯NH2X increase in the order: F < Cl < Br < I and show a good correlation with halogen electronegativities.