title: Isotope effects and heavy-atom tunneling in the Roush allylboration of aldehydes.
abstract: Intermolecular (13)C kinetic isotope effects (KIEs) for the Roush allylboration of p-anisaldehyde were determined using a novel approach. The experimental (13)C KIEs fit qualitatively with the expected rate-limiting cyclic transition state, but they are far higher than theoretical predictions based on conventional transition state theory. This discrepancy is attributed to a substantial contribution of heavy-atom tunneling to the reaction, and this is supported by multidimensional tunneling calculations that reproduce the observed KIEs.
authors.affiliation: Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842, United States.
authors.forename: Mathew J
authors.initials: MJ
authors.lastname: Vetticatt
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Singleton
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D001547:Benzaldehydes / Q000737:chemistry*; D001896:Boron Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D007554:Isotopes; D008962:Models, Theoretical; D015394:Molecular Structure; D013696:Temperature; D013816:Thermodynamics
chemical_list: D000447:Aldehydes; D001547:Benzaldehydes; D001896:Boron Compounds; D007554:Isotopes; C024896:4-anisaldehyde