title: Kinetics of the addition of olefins to Si-centered radicals: the critical role of dispersion interactions revealed by theory and experiment.
abstract: Solution-phase rate constants for the addition of selected olefins to the triethylsilyl and tris(trimethylsilyl)silyl radicals are measured using laser-flash photolysis and competition kinetics. The results are compared with predictions from density functional theory (DFT) calculations, both with and without dispersion corrections obtained from the exchange-hole dipole moment (XDM) model. Without a dispersion correction, the rate constants are consistently underestimated; the errors increase with system size, up to 10(6) s(-1) for the largest system considered. Dispersion interactions preferentially stabilize the transition states relative to the separated reactants and bring the DFT-calculated rate constants into excellent agreement with experiment. Thus, dispersion interactions are found to play a key role in determining the kinetics for addition reactions, particularly those involving sterically bulky functional groups.
authors.affiliation: †Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia, Canada B3H 4R2.|¶Chemistry and Chemical Biology, University of California, Merced, 5200 North Lake Road, Merced, California 95343, United States.
authors.forename: Erin R
authors.initials: ER
authors.lastname: Johnson
authors.affiliation: ‡University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, Ontario, Canada K1Y 4W7.
authors.forename: Owen J
authors.initials: OJ
authors.lastname: Clarkin
authors.affiliation: ¶Chemistry and Chemical Biology, University of California, Merced, 5200 North Lake Road, Merced, California 95343, United States.
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Dale
authors.affiliation: §Department of Chemistry, University of British Columbia, Okanagan, 3247 University Way, Kelowna, British Columbia, Canada V1V 1V7.|⊥National Institute for Nanotechnology, National Research Council of Canada, 11421 Saskatchewan Drive, Edmonton, Alberta, Canada T6G 2M9.
authors.forename: Gino A
authors.initials: GA
authors.lastname: DiLabio
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D007700:Kinetics; D011789:Quantum Theory; D012821:Silanes / Q000737:chemistry*
chemical_list: D000475:Alkenes; D005609:Free Radicals; D012821:Silanes