69961-21-3Relevant academic research and scientific papers
Reactions of carbocations with unsaturated hydrocarbons: Electrophilic alkylation or hydride abstraction?
Mayr, Herbert,Lang, Gabriele,Ofial, Armin R.
, p. 4076 - 4083 (2002)
Benzhydryl cations were used as reference electrophiles to determine the hydride donor reactivities of unsaturated hydrocarbons. The kinetics of the reactions were followed by UV-vis spectroscopy and conductivity measurements, and it was found that the second-order rate constants for the hydride transfer processes were almost independent of the solvents or counterions employed. The rate constants correlate linearly with the previously published empirical electrophilicity parameters E of the benzhydrylium ions. Therefore, the linear free energy relationship log k(20 °C) = s(E + N) could be employed to characterize the hydride reactivities of the hydrocarbons by the nucleophilicity parameters N and s. The similarity of the slopes s for hydride donors and π-nucleophiles allows a direct comparison of the reactivities of these different functional groups based on their nucleophilicity parameters N. Since nucleophilicity parameters of -5 N 0 have been found for a large variety of allylic and bisallylic hydride donors, a rule of thumb is derived that hydride transfer processes may compete with carbon-carbon bond-forming reactions when carbocations are combined with olefins of π-nucleophilicity N 0.
Visible Absorption Spectra and Two-Photon Photodissociation of Halobenzene Cations in Solid Argon
Keelan, Brian W.,Andrews, Lester
, p. 829 - 832 (2007/10/02)
Matrix photoionization experiments with bromobenzene, chlorobenzene, and fluorobenzene precursors produced absorptions dur to bromobenzene cation at 505 +/- 5 nm, chlorobenzene cation at 470 +/- 2 nm, and fluorobenzene cation at 431 +/- 1 nm, respectively, in excellent agreement with gas-phase photodissociation and photoelectron spectra.Two-photon dissosiation of the bromobenzene cation in solid argon was affected by photolysis in the very strong visible n2 ->? charge-transfer electronic transition, as found in earlier gas-phase work.The lack of significant two-photon dissociation of fluorobenzene cation is attributed to lower oscillator strength for the ?->? transition corresponding to absorption of the first photon.
Absorption Spectra and Photochemical Rearrangement of Cycloheptatriene Cation to Toluene Cation in Solid Argon
Andrews, Lester,Keelan, Brian W.
, p. 5732 - 5736 (2007/10/02)
The toluene and cycloheptatriene cations have been produced and trapped in solid argon by matrix photoionization techniques.Toluene experiments gave a photosensitive 430-nm absorption and weak 480-nm band, the cycloheptatriene studies yielded a broad 480-nm absorption and a weak 430-nm band; these matrix bands are slightly red shifted the photodissociation spectra (PDS) peaks for the corresponding parent cations.Visible photolysis in cycloheptatriene experiments decreased the 480-nm band and increased the 430-nm absorption, indicating that cycloheptatriene cation can be photochemically rearrnged to toluene cation.The toluene cation absorption bandwidth is more than an order of magnitude less in solid argon than in ICR experiments; this may be due to quenching excess vibrational energy in the ground-state ion by the matrix and / or a reduction in the rate of internal conversion from the excited-state ion in the matrix owing to rapid relaxation to lower vibrational levels of the excited state where the density of states for vibronic coupling is less.The reduced photolysis rate of toluene cation in the matrix is consistent with the latter point and a efficient removal of vibrational energy from the vibrationally excited ground-state ion resulting from internal conversion.
