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Université de Fribourg

The bisketene radical cation and its formation by oxidative ring-Opening of cyclobutenedione

Piech, Krzysztof ; Bally, Thomas ; Allen, Annette D. ; Tidwell, Thomas T.

In: The Journal of Organic Chemistry, 2013, vol. 78, no. 7, p. 2908–2913

Parent cyclobutenedione 1 was photolyzed and ionized in an Ar matrix at 10K. The bisketene 2 that results in both cases (in the form of its radical cation after ionization) was characterized by its IR spectrum and by high-level quantum chemical calculations. Experiment and theory show that the neutral bisketene has only a single conformation where the two ketene moieties are nearly perpendicular,...

Université de Fribourg

Influence of connector groups on the interactions of substituents with carbon-centered radicals

Menon, Ambili S. ; Bally, Thomas ; Radom, Leo

In: The Journal of Physical Chemistry, 2012, vol. 116, no. 41, p. 10203–10208

High-level G3X(MP2)-RAD calculations have been carried out to examine the effect of interposing a “connector” group (W) on the interaction between a substituent (X) and the radical center in carbon-centered radicals (•CH₂–W–X). The connector groups include −CH₂–, −CH═CH–, −C≡C–, −p-C₆H₄–, −m-C₆H₄–, and −o-C₆H₄–,...

Université de Fribourg

Synthesis and rotation barriers in 2, 6-Di-(o-anisyl) anisole

Yamamoto, Takuhei ; Chen, Pi-Yu ; Lin, Guangxin ; Błoch-Mechkour, Anna ; Jacobsen, Neil E. ; Bally, Thomas ; Glass, Richard S.

In: Journal of Physical Organic Chemistry, 2012, p. -

Variable temperature ¹H NMR spectroscopic studies of 2, 6-di(o-anisyl) anisole show syn and anti atropisomers at low temperature. The barrier for interconverting these isomers by rotation about the aryl-aryl bond, found by fitting the experimental data, is 41.2 kJ/mol.

Université de Fribourg

Photolysis of ortho-nitrobenzylic derivatives: the importance of the leaving group

Šolomek, Tomáš ; Mercier, Sébastien ; Bally, Thomas ; Bochet, Christian G.

In: Photochemical & Photobiological Sciences, 2012, vol. 11, no. 3, p. 548-555

Quantum yields for the photoinduced release of seven different commonly used leaving groups (LGs) from the o-nitroveratryl protecting group were measured. It was found that these quantum yields depend strongly on the nature of the LGs. We show that the quantum efficiency with which the LGs are released correlates with the stabilization that these LGs provide to o-nitrobenzyl-type radicals because...

Université de Fribourg

Quantum-Chemical simulation of ¹H NMR spectra. 2. comparison of DFT-Based procedures for computing proton–proton coupling constants in organic molecules

Bally, Thomas ; Rablen, Paul R.

In: The Journal of Organic Chemistry, 2011, vol. 76, no. 12, p. 4818–4830

The performance of 250 different computational protocols (combinations of density functionals, basis sets and methods) was assessed on a set of 165 well-established experimental ¹H–¹H nuclear coupling constants (JH–H) from 65 molecules spanning a wide range of “chemical space”. Thereby we found that, if one uses core-augmented basis sets and allows for linear scaling...

Université de Fribourg

Dimer radical cations of indole and indole-3-carbinol: localized and delocalized radical cations of diindolylmethane

Błoch-Mechkour, Anna ; Bally, Thomas ; Marcinek, Andrzej

In: The Journal of Physical Chemistry A, 2011, vol. 115, no. 26, p. 7700–7708

Extending our previous study on the title species (J. Phys. Chem. A2010, 114, 6787), we investigated the dimer cations that are formed on oxidation of the glucobrassin derivatives indole-3-carbinol (I3C) and diindolylmethane (DIM) and of parent indole (I). Radiolysis in ionic liquid and Ar matrices shows that, at sufficiently high concentrations and/or on...

Université de Fribourg

Effect of substituents on the stabilities of multiply-substituted carbon-centered radicals

Menon, Ambili S. ; Henry, David J. ; Bally, Thomas ; Radom, Leo

In: Organic & Biomolecular Chemistry, 2011, vol. 9, p. 3636-3657

The bond dissociation energies (BDEs) and radical stabilization energies (RSEs) which result from 166 reactions that lead to carbon-centered radicals of the type ˙CH₂X, ˙CHXY and ˙CXYZ, where X, Y and Z are any of the fourteen substituents H, F, Cl, NH₂, OH, SH, CH=CH₂, C≡CH, BH₂, CHO, COOH, CN, CH₃, and CF₃, were calculated using spin-restricted and -unrestricted variants of the...

Université de Fribourg

Synthesis and structure of m-terphenyl thio-, seleno-, and telluroethers

Zakai, Uzma I. ; Błoch-Mechkour, Anna ; Jacobsen, Neil E. ; Abrell, Leif ; Lin, Guangxin ; Nichol, Gary S. ; Bally, Thomas ; Glass, Richard S.

In: Journal of Organic Chemistry, 2011, vol. 75, no. 24, p. 8363–8371

Several routes for the synthesis of m-terphenyl thio-, seleno-, and telluroethers were investigated. m-Terphenyl iodides react with diphenyl diselenides or ditellurides (CsOH·H₂O, DMSO, 110 °C) to give the desired compounds in 19−84% yield which significantly extends the previously reported such reactions because o-benzyne cannot be an intermediate as previously...

Université de Fribourg

Spectroscopic and computational studies on the rearrangement of ionized [1.1.1]propellane and some of its valence isomers: the key role of vibronic coupling

Müller, Beat ; Bally, Thomas ; Pappas, Robert ; Williams, Ffrancon

In: Journal of the American Chemical Society, 2010, vol. 132, no. 41, p. 14649–14660

The [1.1.1]propellane radical cation 1•+, generated by radiolytic oxidation of the parent compound in argon and Freon matrices at low temperatures, undergoes a spontaneous rearrangement to form the distonic 1,1-dimethyleneallene (or 2-vinylideneallyl) radical cation 3•+ consisting of an allyl radical substituted at the 2-position by a vinyl...

Université de Fribourg

Radicals and radical ions derived from indole, indole-3-carbinol and diindolylmethane

Błoch-Mechkour, Anna ; Bally, Thomas ; Sikora, Adam ; Michalski, Radosław ; Marcinek, Andrzej ; Gębicki, Jerzy

In: The Journal of Physical Chemistry A, 2010, vol. 114, no. 25, p. 6787–6794

The primary products, i.e., the radical cations and radicals obtained on oxidation of the glucobrassicin metabolites (and dietary supplements), indole-3-carbinol (I3C) and diindolylmethane (DIM), and those from parent indole (I) are characterized in an ionic liquid and in Ar matrices. The radical cations of I and I3C are stable toward (photo)deprotonation under these conditions, but the resulting...