title: Mechanism of α-ketol-type rearrangement of benzoin derivatives under basic conditions.
abstract: The mechanism of base-catalyzed rearrangement of ring-substituted benzoins in aqueous methanol was examined by kinetic and product analyses. Substituent effects on the rate and equilibrium constants revealed that the kinetic process has a different electron demand compared to the equilibrium process. Reactions in deuterated solvents showed that the rate of H/D exchange of the α-hydrogen is similar to the overall rate toward the equilibrium state. A proton-inventory experiment using partially deuterated solvents showed a linear dependence of the rate on the deuterium fraction of the solvent, indicating that only one deuterium isotope effect contributes to the overall rate process. All these results point to a mechanism in which the rearrangement is initiated by the rate-determining α-hydrogen abstraction rather than a mechanism with initial hydroxyl hydrogen abstraction as in the general α-ketol rearrangement.
authors.affiliation: Department of Chemistry and the Research Center for Smart Molecules, Rikkyo University, Nishi-Ikebukuro, Toshima-ku, 171-8501 Tokyo, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Karino
authors.forename: Daiki
authors.initials: D
authors.lastname: Kubouchi
authors.forename: Kazuki
authors.initials: K
authors.lastname: Hamaoka
authors.forename: Shintaro
authors.initials: S
authors.lastname: Umeyama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamataka
mesh_terms: D001573:Benzoin / Q000737:chemistry*; D002384:Catalysis; D006878:Hydroxides / Q000737:chemistry*; D007700:Kinetics; D000432:Methanol / Q000737:chemistry; D015394:Molecular Structure; D017680:Potassium Compounds / Q000737:chemistry*
chemical_list: D006878:Hydroxides; D017680:Potassium Compounds; D001573:Benzoin; C029943:potassium hydroxide; D000432:Methanol