25807-60-7Relevant articles and documents
Evidence for significant through-space and through-bond electronic coupling in the 1,4-diphenylcyclohexane-1,4-diyl radical cation gained by absorption spectroscopy and DFT calculations
Ikeda, Hiroshi,Hoshi, Yosuke,Namai, Hayato,Tanaka, Futoshi,Goodman, Joshua L.,Mizuno, Kazuhiko
, p. 9207 - 9215 (2008/12/21)
Photoinduced single-electron-transfer promoted oxidation of 2,5-diphenyl-l,5-hexadiene by using N-methylquinolinium tetrafluoroborate/ biphenyl co-sensitization takes place with the formation of an intense electronic absorption band at 476 nm, which is attributed to the 1,4-diphenylcyclohexane-1,4-diyl radical cation. The absorption maximum (λob) of this transient occurs at a longer wavelength than is expected for either the cumyl radical or the cumyl cation components. Substitution at the para positions of the phenyl groups in this radical cation by CH3O, CH3, F, Cl, and Br leads to an increasingly larger redshift of λob. A comparison of the ρ value, which was obtained from a Hammett plot of the electronic transition energies of the radical cations versus σ+, with that for the cumyl cation shows that the substituent effects on the transition energies for the 1,4-diarylcyclohexane-1,4-diyl radical cations are approximately one half of the substituent effects on the transition energies of the cumyl cation. The observed substitu_ent-induced redshifts of λob and the reduced sensitivity of λob to substituent changes are in accordance with the proposal that significant through-space and -bond electronic interactions exist between the cumyl radical and the cumyl cation moieties of the 1,4-diphenylcyclohexane-1,4-diyl radical cation. This proposal gains strong support from the results of density functional theory (DFT) calculations. Moreover, the results of time-dependent DFT calculations indicate that the absorption band at 476 nm for the 1,4-diphenylcyclohexane-1,4-diyl radical cation corresponds to a SOMO-3-SOMO transition.
Deuterium Isotope Effects on the Carbon-13 Chemical Shifts in 2-Substituted 2-Norbornyl Cations
Servis, Kenneth L.,Domenick, Robert L.,Forsyth, David A.,Pan, Yi
, p. 7263 - 7270 (2007/10/02)
Deuterium isotope effects on 13C chemical shifts have been examined as a function of location of deuterium in the C3-exo or C3-endo positions and as a function of increasing electron demand in the series 2-norbornanone, 2-aryl-2-norb
Substituent Effect on the Stability of Benzyl Cation in the Gas Phase
Mishima, Masaaki,Arima, Kiyoshi,Usui, Satoshi,Fujio, Mizue,Tsuno, Yuho
, p. 1047 - 1050 (2007/10/02)
Chloride ion affinities of substituted benzyl cations in the gas phase have been determined by means of an ICR mass spectrometer.The substituent effect has been analyzed in terms of the LArSr Eq., giving a p=13.6 and r+=1.31.
Conformational Dependence of Isotope Effects for Hyperconjugating Methyl Groups. Nonadditivity of NMR Isotope Shifts in Benzylic Ions
Forsyth, David A.,Lucas, Peter,Burk, Robert M.
, p. 240 - 245 (2007/10/02)
Deuterium substitution in the methyl groups induces long-range downfield shifts in 13C NMR signals of the ortho and para positions of the phenyldimethylcarbenium ion.Similar downfield isotope shifts occur in 19F signals of (p-fluorophenyl)carbenium ions upon deuteration of α-methyl groups.These NMR isotope shifts are analogous to secondary β-deuterium isotope effects on rates and equilibria and arise from hyperconjugative interactions.The effects of substituting entire CD3 groups for CH3 groups are additive, but the effects of deuterium substitution within a methyl group are not additive.The nonadditive behavior is attributed to unequal populations of the possible methyl conformation for partially deuterated methyl groups, so that each C-H(D) bond is not equally involved in hyperconjugation.This interpretation is supported by the observation of an isotope effect on the vicinal 1H-19F coupling constant in the phenylmethylfluorocarbenium ion, PhCFCH3+.
