title: Two-dimensional free-energy surface on the exchange reaction of alkyl chloride/chloride using the QM/MM-MC method.
abstract: Two-dimensional free-energy surfaces are calculated for alkyl chloride/chloride exchange/inversion reactions: Cl(-)+RCl (R=Me and t-Bu) surrounded by one hundred H(2)O molecules as a model of solvent. The methodology of free-energy calculation by perturbation theory based on a mixed-Hamiltonian model (QM/MM) combined with Monte Carlo sampling of the solvent configurations was used to obtain the changes in solvation free energy. We devised a special procedure to analyze the two-dimensional free-energy surfaces to gain unique insight into the differences in the reaction mechanisms between the two systems. The inversion reaction path for R=t-Bu on the free-energy surface is found to proceed in an asynchronous way within a concerted framework via the ion-pair region. This is in contrast to the R=Me system that proceeds as a typical S(N)2 reaction.
authors.affiliation: Center for Quantum Life Sciences, and Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, 739-8526, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ohisa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamataka
authors.forename: Michel
authors.initials: M
authors.lastname: Dupuis
authors.forename: Misako
authors.initials: M
authors.lastname: Aida
mesh_terms: D002712:Chlorides / Q000737:chemistry*; D003198:Computer Simulation; D004735:Energy Transfer; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry*; D008956:Models, Chemical; D011789:Quantum Theory; D013499:Surface Properties; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D002712:Chlorides; D006843:Hydrocarbons, Chlorinated; D014867:Water