OPLS-AA force field parameters have been developed and validated for use in the simulation of 70 unique combinations of ionic liquids (IL) featuring 1-alkyl-3-methylimidazolium [RMIM] (R = Me, Et, Bu, Hex, Oct), N-alkylpyridinium [RPYR], and choline cations, along with Cl-, PF6-, BF4-, NO3-, AlCl4-, AlCl7-, TfO-, saccharinate, and  acesulfamate anions. The new parameters were fit to reproduce experimental condensed-phase structural and thermodynamic properties. Monte Carlo (MC) simulations of the ILs gave relative deviations from experimental densities and heats of vaporization of 1-3% over a wide temperature range. Mixed quantum and molecular mechanics (QM/MM) MC calculations featuring our custom force field and free-energy perturbation theory were used to elucidate how ILs operate to enhance rates and/or shift mechanisms for important reactions classes: Diels-Alder, Kemp eliminations, aromatic nucleophilic substitutions, and base-induced �-eliminations. The parameters presented have been shown to be highly accurate for organic reactions in a variety of cation/anion combinations.

Development of OPLS-AA force field parameters for QM/MM ionic liquid simulations

244th National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.