Ion-Pair S N 2 Reaction of OH - and CH 3 Cl: Activation Strain Analyses of Counterion and Solvent Effects.

We have theoretically studied the non-identity S _N 2 reactions of M _n OH ^(n-1) +CH ₃ Cl (M ⁺ =Li ⁺ , Na ⁺ , K ⁺ , and MgCl ⁺ ; n=0, 1) in the gas phase and in THF solution at the OLYP/6-31++G(d,p) level using polarizable continuum model (PCM) implicit solvation. We want to explore and understand the effect of the metal counterion M ⁺ and solvation on the reaction profile and the stereoselectivity of these processes. To this end, we have explored the potential energy surfaces of the backside (S _N 2-b) and frontside (S _N 2-f) pathways. To explain the computed trends, we have carried out analyses with an extended activation strain model (ASM) of chemical reactivity that includes the treatment of solvation effects.
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