Showing papers by "Thomas Bally published in 2002"
TL;DR: The present work represents the first attempt to quantitate the small contributions that the cis rotamers make to the room-temperature equilibrium compositions of the two o-substituted benzaldehydes.
Abstract: The cis and trans conformers of benzaldehydes substituted in the o- or m-positions by Cl or CN can be differentiated by IR spectroscopy in Argon matrices. Partial photochemical rotamerization allows assignment of the IR bands and establishment of their relative intensities in pairs of rotamers, which permits, in turn, quantitation of equilibrium compositions prior to photolysis. The observed spectra and equilibrium compositions are in very good agreement with the predictions of vibrational spectra and free energy differences from B3LYP/6-31G * calculations. The present work represents the first attempt to quantitate the small contributions that the cis rotamers make to the roomtemperature equilibrium compositions of the two o-substituted benzaldehydes. The results for the m-substituted derivatives are compared to earlier estimates based on other methods.
18 citations
TL;DR: Alkoxychlorocarbenes (ROCCl, R = benzyl, cyclohexyl, and 1-octyl) were generated from the corresponding diazirines in acetonitrile, dichloroethane, benzene, and pentane solutions at 25 as discussed by the authors.
Abstract: Alkoxychlorocarbenes (ROCCl, R = benzyl, cyclohexyl, and 1-octyl) were generated from the corresponding diazirines in acetonitrile, dichloroethane, benzene, cyclohexane, and pentane solutions at 25...
11 citations
TL;DR: The photochemistry of the pyrazolo[1,2-a]benzotriazole 1b and its dimethyl derivative 1c was studied in argon matrices and in solution to rationalize the mechanism of the photocyclization and its thermal back-reaction.
Abstract: The photochemistry of the pyrazolo[1,2-a]benzotriazole 1b and its dimethyl derivative 1c was studied in argon matrices at 12 K and in solution at 190 K. On irradiation at 365 nm, 1b and 1c undergo ring closure to yield the triazasemibullvalenes 2b and 2c, respectively, which were identified unambiguously by NMR and IR spectroscopy. This novel type of cyclization is reversed on warming or by irradiation at 313 nm. Quantum chemical calculations serve to model the observed IR and UV spectra and to rationalize the mechanism of the photocyclization and its thermal back-reaction.
9 citations