(291g) Solvent Reaction Coordinate for an SN2 Reaction

We study the prototypical S_N2 reaction Cl^- + CH₃Cl → CH₃Cl + Cl^- in water using QM/MM computer simulations with transition path sampling [1] and inertial likelihood maximization [2]. We have identified a new solvent coordinate that improves upon the original solute-only atom-exchange coordinate used in the classic analysis by Chandrasekhar et al. [3]. The new solvent coordinate quantifies instantaneous solvent induced polarization relative to equilibrium charge density at each point along the reaction pathway. We will present free energy surfaces, transmission coefficients, and a committor test for a selection of solute and solvent coordinates.

[1] P. G. Bolhuis, D. Chandler, C. Dellago, and P. L. Geissler, Ann. Rev. Phys. Chem. 53, 291 (2002).

[2] B. Peters, Chem. Phys. Lett. 554, 248 (2012).

[3] J. Chandrasekhar, S. F. Smith, and W. L. Jorgensen, J. Am. Chem. Soc. 107, 154 (1985).