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 Cl- + CH3I --> ClCH3 + I-  SN2  Reaction Dynamics

This study is part of a research collaboration with The Roland Wester research group, University of Freiburg, Germany. Both direct and indirect reaction mechanisms are observed in the trajectories. The direct reaction occurs via the traditional SN2 mechanism with Cl- colliding backside with direct displacement of I-.  The indirect reaction occurs via a CH3 rotation, roundabout mechanism in which Cl- strikes the CH3-moiety causing it to rotate around the I-atom and Cl- displacing I- after one CH3 revolution with the backside of the CH3-moiety positioned next to Cl-. A small fraction of this indirect reaction occurs via multiple CH3 revolution. The following are animations of representative trajectories for the two mechanisms, for collisions with a relative translational energy of 46.1 kcal/mol, a CH3I rotational and vibrational temperature of 300K and an impact parameter of 0.5 Å.

Trajectories Animated

Direct reaction:

Indirect reaction with one CH3 rotation:

Indirect reaction with two CH3 rotations:

Non-reactive with formation of both pre-reaction and post-reaction complexes, and barrier recrossing: