Unusual reaction paths of SN2 nucleophile substitution reactions CH4 + H− → CH4 + H− and CH4 + F− → CH3F + H−: Quantum chemical calculations

- High level quantum chemical calculations are performed for two SN2 reactions.
- The calculated gradient reaction pathways for reactions have an unusual behavior.
- An unusual saddle point of index two lies on the gradient reaction path.
- VRI points have been detected by using Newton trajectories for the reaction path.
- An infinite flow of gradient lines emanates at three equivalent product minima.

Quantum chemical (CCSD(full)/6-311++G(3df,3pd), CCSD(T)(full)/6-311++G(3df,3pd)) and density function theory (B3LYP/6-311++G(3df,3pd)) calculations were performed for the SN2 nucleophile substitution reactions CH4 + H− → CH4 + H− and CH4 + F− → CH3F + H−. The calculated gradient reaction pathways for both reactions have an unusual behavior. An unusual stationary point of index 2 lies on the gradient reaction path. Using Newton trajectories for the reaction path, we can detect VRI point at which the reaction path branches.