title: Identity SN2 reactions X- + CH3X --> XCH3 + X- (X=F, Cl, Br, and I) in vacuum and in aqueous solution: a valence bond study.
abstract: The recently developed (L. Song, W. Wu, Q. Zhang, S. Shaik, J. Phys. Chem. A 2004, 108, 6017) valence bond method coupled with a polarized continuum model (VBPCM) has been applied to the identity SN2 reaction of halides in the gas phase and in aqueous solution. The barriers computed at the level of the breathing orbital VB method (P. C. Hiberty, J. P. Flament, E. Noizet, Chem. Phys. Lett. 1992, 189, 259), BOVB and VBPCM//BOVB, are comparable to CCSD(T) and CCSD(T)//PCM results and to experimentally derived barriers in solution (W. J. Albery, M. M. Kreevoy, Adv. Phys. Org. Chem. 1978, 16, 85). The reactivity parameters needed to apply the valence bond state correlation diagram (VBSCD) method (S. Shaik, J. Am. Chem. Soc. 1984, 106, 1227), were also determined by VB calculations. It has been shown that the reactivity parameters along with their semiempirical derivations provide a satisfactory qualitative and quantitative account of the barriers.
authors.affiliation: Department of Chemistry, Center for Theoretical Chemistry and State Key Laboratory for Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen, Fujian 361005, China.
authors.forename: Lingchun
authors.initials: L
authors.lastname: Song
authors.forename: Wei
authors.initials: W
authors.lastname: Wu
authors.forename: Philippe C
authors.initials: PC
authors.lastname: Hiberty
authors.forename: Sason
authors.initials: S
authors.lastname: Shaik
mesh_terms: D003198:Computer Simulation; D006219:Halogens / Q000737:chemistry*; D006842:Hydrocarbons, Brominated / Q000737:chemistry; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry; D006846:Hydrocarbons, Halogenated / Q000737:chemistry*; D006847:Hydrocarbons, Iodinated / Q000737:chemistry; D008737:Methyl Chloride / Q000737:chemistry; D008956:Models, Chemical; D012996:Solutions; D014618:Vacuum; D014867:Water
chemical_list: D006219:Halogens; D006842:Hydrocarbons, Brominated; D006845:Hydrocarbons, Fluorinated; D006846:Hydrocarbons, Halogenated; D006847:Hydrocarbons, Iodinated; D012996:Solutions; D014867:Water; C029999:fluoromethane; C005218:methyl bromide; D008737:Methyl Chloride; C014055:methyl iodide