title: Preparation, structural characterization, and thermochemistry of an isolable 4-arylphenoxyl radical.
abstract: The preparation and full characterization of the 4-(nitrophenyl)phenoxyl radical, 2,6-di-(t)butyl-4-(4'-nitrophenyl) phenoxyl radical ((t)Bu2NPArO(•)) is described. This is a rare example of an isolable and crystallographically characterized phenoxyl radical and is the only example in which the parent phenol is also crystallographically well-defined. Analysis of EPR spectra indicates some spin delocalization onto the secondary aromatic ring and nitro group. Equilibrium studies show that the corresponding phenol has an O-H bond dissociation free energy (BDFE) of 77.8 ± 0.5 kcal mol(-1) in MeCN (77.5 ± 0.5 kcal mol(-1) in toluene). This value is higher than related isolated phenoxyl radicals, making this a useful reagent for hydrogen atom transfer (HAT) studies. Additional thermochemical and spectroscopic parameters are also discussed.
authors.affiliation: Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Porter
authors.forename: Werner
authors.initials: W
authors.lastname: Kaminsky
authors.forename: James M
authors.initials: JM
authors.lastname: Mayer
mesh_terms: D018360:Crystallography, X-Ray; D008958:Models, Molecular; D009574:Nitro Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D014050:Toluene / Q000737:chemistry*
chemical_list: C000597335:2,6-di-(t)butyl-4-(4'-nitrophenyl)phenoxyl radical; C000597334:4-(nitrophenyl)phenoxyl radical; D009574:Nitro Compounds; D010636:Phenols; C042329:phenoxy radical; D014050:Toluene