Unconventional SN2 retention pathways induced by complex formation: High-level dynamics investigation of the NH2 - + CH3I polyatomic reaction.

Abstract

Investigations on the dynamics of chemical reactions have been a hot topic for experimental and theoretical studies over the last few decades. Here, we carry out the first high-level dynamical characterization for the polyatom-polyatom reaction between NH2 - and CH3I. A global analytical potential energy surface is developed to describe the possible pathways with the quasi-classical trajectory method at several collision energies. In addition to SN2 and proton abstraction, a significant iodine abstraction is identified, leading to the CH3 + [NH2⋯I]- products. For SN2, our computations reveal an indirect character as well, promoting the formation of [CH3⋯NH2] complexes. Two novel dominant SN2 retention pathways are uncovered induced by the rotation of the CH3 fragment in these latter [CH3⋯NH2] complexes. Moreover, these uncommon routes turn out to be the most dominant retention paths for the NH2 - + CH3I SN2 reaction.