Identity SN2 reactions X- + CH3X --> XCH3 + X- (X=F, Cl, Br, and I) in vacuum and in aqueous solution: a valence bond study.
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.
Song
Lingchun
L
Department of Chemistry, Center for Theoretical Chemistry and State Key Laboratory for Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen, Fujian 361005, China.
Wu
Wei
W
Hiberty
Philippe C
PC
Shaik
Sason
S
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
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