Uncovering an oxide ion substitution for the OH⁻ + CH₃F reaction

Abstract

Theoretical investigations on chemical reactions allow us to understand the dynamics of the possible pathways and identify new unexpected routes. Here, we develop a global analytical potential energy surface (PES)...

Quantitative Dynamics of the Paradigmatic SN2 reaction OH− + CH3F on a Chemically Accurate Full-Dimensional Potential Energy Surface

“…The two reactants first form an ionic complex HO − ‧‧‧CH3F, an important intermediate that is directly connected by all transition states, TS, TS1, TS2, TS3, and TS4. At the CCSD(T)-F12a/AVTZ level, the calculated electronic energy is −13.90 kcal/mol, consistent with the current PIP-NN PES value, −13.82 kcal/mol, the PIP PES value, −14.05 kcal/mol 21 and the benchmark result, −13.76 kcal/mol. 11,13 As shown in The Walden-inversion transition state, TS1, is −2.85 and −2.78 kcal/mol at the CCSD(T)-F12a/AVTZ level and on the PIP-NN PES, respectively, in good agreement with the benchmark result, −2.60 kcal/mol.…”

“…The integral cross sections (ICSs), differential cross sections (DCSs), product energy partitioning, and microscopic mechanisms are calculated and analyzed, and used to validate the direct dynamical results by Hase and coworkers 6 and the results computed on the PIP PES. 21 A new route to H2O and CH2F − was revealed on this accurate PES: the trajectory may not follow the MEPs to undergo the transition states or the CH2F − ‧‧‧H2O complex, which has not been reported in previous investigations.…”

“…In the evolving process from TS1 to CH3OH‧‧‧F − , the trajectories may avoid the MEP due to an inertial force, namely, non-MEP dynamics. 6,21 The post-reaction well CH3OH‧‧‧F − is a hydrogen-bonded complex in the exit channel and the global minimum on the PES, 50.16 kcal/mol lower than the reactants. CH3OH‧‧‧F − can directly dissociate to two distinct products, F − + CH3OH (the conventional SN2, R1) and HF + CH3O − (the O 2− substitution, R4).…”

“…In addition to confirming the dominance of the non-MEP trajectories for the F − + CH3OH channel, most importantly, they revealed a novel exothermic reaction pathway to the unexpected products, HF + CH3O − . 21 The dynamical results are largely influenced by the PES quality, 18,22,23 which is determined by the level of the electronic structure calculation and the representation function form. Analytical PESs can be developed efficiently by various fitting techniques based on tens or even hundreds of thousands of configurations at a reasonably high level of theory, such as coupled-cluster and configuration interaction theories, for gas-phase reactions.…”

Proton transfer-induced competing product channels of microsolvated Y−(H2O)n + CH3I (Y = F, Cl, Br, I) reactions

“…This channel has been reported recently by the Czako group for the HO − + CH 3 F → CH 3 O − + HF reaction via a quasi-classical dynamic simulation on a full-dimensional potential energy surface. 48 For the titled reaction, the PT CH3 channel can occur without water molecules, but HO − -S N 2 and OIS channels occur only if water molecules are involved.…”