2018 AIChE Annual Meeting

(173a) Solvent Reaction Coordinate for an SN2 Reaction

Authors

Christian Leitold - Presenter, University of Vienna
Christopher J. Mundy, Pacific Northwest National Laboratory
Marcel D. Baer, Pacific Northwest National Laboratory
Gregory K. Schenter, Pacific Northwest National Laboratory
Baron Peters, University of California Santa Barbara
We study the prototypical SN2 reaction Cl- + CH3Cl → CH3Cl + Cl- in water using QM/MM computer simulations with transition path sampling [1] and inertial likelihood maximization [2], implemented in CP2K [3]. We have identified a new solute coordinate and a new solvent coordinate that both improve upon the original atom-exchange coordinate used in the classic analysis by Chandrasekhar et al. [4, 5]. The new solvent coordinate quantifies instantaneous solvent induced polarization relative to equilibrium charge density at each point along the reaction pathway. The new solute coordinate quantifies the out-of-plane motion of the central -CH3- fragment. We will present free energy surfaces, transmission coefficients, and an analysis of the friction spectrum for the optimized 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. VandeVondele, M. Krack, F. Mohamed, M. Parrinello, T. Chassaing, and J. Hutter, Comput. Phys. Commun. 167, 103 (2005).

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

[5] B. J. Gertner, Kent R. Wilson, D. A. Zichi, S. Lee, and J. T. Hynes, Faraday Discuss. Chem. Soc. 85, 297-308 (1988).