title: EPR investigation of zinc/iodine exchange between propargyl iodides and diethylzinc: detection of propargyl radical by spin trapping.
abstract: The production of propargyl radicals in the reaction of dialkylzincs with propargyl iodides in nondegassed medium was investigated by EPR using tri-tert-butylnitrosobenzene (TTBNB) as a spin trap. The radical mechanism and the nature of the observed species were confirmed by the trapping of propargyl radicals generated by an alternative pathway: i.e., upon irradiation of propargyl iodides in the presence of hexa-n-butyldistannane. In dialkylzinc-mediated experiments a high concentration of adduct was instantaneously observed, whereas no spontaneous production of spin adduct was detected in a blank experiment performed with the propargylic iodide and TTBNB in the absence of diethylzinc. Under irradiation in the presence of distannane, two different species were observed at the very beginning of the irradiation; the nitroxide resulting from the trapping of propargyl radical at the propargyl carbon remained the only species detected after irradiating for several minutes. The absence of adducts resulting from the trapping of allenyl canonical forms was supported by DFT calculations and by the preparation of an authentic sample.
authors.affiliation: Equipes CMO, Aix-Marseille Université, CNRS, Institut de Chimie Radicalaire UMR 7273, 13397 Cedex 20, Marseille, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Maury
authors.forename: Suribabu
authors.initials: S
authors.lastname: Jammi
authors.forename: François
authors.initials: F
authors.lastname: Vibert
authors.forename: Sylvain R A
authors.initials: SR
authors.lastname: Marque
authors.forename: Didier
authors.initials: D
authors.lastname: Siri
authors.forename: Laurence
authors.initials: L
authors.lastname: Feray
authors.forename: Michèle
authors.initials: M
authors.lastname: Bertrand
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D006847:Hydrocarbons, Iodinated / Q000737:chemistry*; D007455:Iodine / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D011789:Quantum Theory; D015032:Zinc / Q000737:chemistry*
chemical_list: D000480:Alkynes; D005609:Free Radicals; D006847:Hydrocarbons, Iodinated; D009942:Organometallic Compounds; D007455:Iodine; D015032:Zinc