title: Pentakis(trifluoromethyl)phenyl, a sterically crowded and electron-withdrawing group: synthesis and acidity of pentakis(trifluoromethyl)benzene, -toluene, -phenol, and -aniline.
abstract: A general route to functionalized pentakis(trifluoromethyl)phenyl (C6(CF3)5) derivatives, promising building blocks for designing novel stable carbenes, radical species, superacids, weakly coordinating anions and other practically and theoretically useful species, is presented. This pertrifluoromethylation route proceeds via conveniently pregenerated (trifluoromethyl)copper (CF3Cu) species in DMF, stabilized by addition of 1,3-dimethyl-2-imidazolidinone (DMI). These species react with hexaiodobenzene at ambient temperature to give the potassium pentakis(trifluoromethyl)phenoxide along with hexakis(trifluoromethyl)benzene and pentakis(trifluoromethyl)benzene in a combined yield of 80%. A possible reaction pathway explaining the formation of pentakis(trifluoromethyl)phenoxide is proposed. Pentakis(trifluoromethyl)phenol gives rise to easily functionalized pentakis(trifluoromethyl)chlorobenzene and pentakis(trifluoromethyl)aniline. Pertrifluoromethylation of pentaiodochlorobenzene and pentaiodotoluene allows straightforward access to pentakis(trifluoromethyl)chlorobenzene and pentakis(trifluoromethyl)toluene, respectively. XRD structures of several C6(CF3)5 derivatives were determined and compared with the calculated structures. Due to the steric crowding the aromatic rings in all C6(CF3)5 derivatives are significantly distorted. The gas-phase acidities (Delta Gacid) and pKa values in different solvents (acetonitrile (AN), DMSO, water) for the title compounds and a number of related compounds have been measured. The origin of the acidifying effect of the C6(CF3)5 group has been explored using the isodesmic reactions approach.
authors.affiliation: University of Tartu, Institute of Chemistry, 2 Jakobi St., 51014 Tartu, Estonia.
authors.forename: Agnes
authors.initials: A
authors.lastname: Kütt
authors.forename: Valeria
authors.initials: V
authors.lastname: Movchun
authors.forename: Toomas
authors.initials: T
authors.lastname: Rodima
authors.forename: Timo
authors.initials: T
authors.lastname: Dansauer
authors.forename: Eduard B
authors.initials: EB
authors.lastname: Rusanov
authors.forename: Ivo
authors.initials: I
authors.lastname: Leito
authors.forename: Ivari
authors.initials: I
authors.lastname: Kaljurand
authors.forename: Juta
authors.initials: J
authors.lastname: Koppel
authors.forename: Viljar
authors.initials: V
authors.lastname: Pihl
authors.forename: Ivar
authors.initials: I
authors.lastname: Koppel
authors.forename: Gea
authors.initials: G
authors.lastname: Ovsjannikov
authors.forename: Lauri
authors.initials: L
authors.lastname: Toom
authors.forename: Masaaki
authors.initials: M
authors.lastname: Mishima
authors.forename: Maurice
authors.initials: M
authors.lastname: Medebielle
authors.forename: Enno
authors.initials: E
authors.lastname: Lork
authors.forename: Gerd-Volker
authors.initials: GV
authors.lastname: Röschenthaler
authors.forename: Ilmar A
authors.initials: IA
authors.lastname: Koppel
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Kolomeitsev
mesh_terms: D003198:Computer Simulation; D018360:Crystallography, X-Ray; D004583:Electrons; D006845:Hydrocarbons, Fluorinated / Q000138:chemical synthesis* / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D006845:Hydrocarbons, Fluorinated