Inner-Phase Reaction Dynamics: The Influence of Hemicarcerand Polarizability and Shape on the Potential Energy Surface of an Inner-Phase Reaction
作者:Sigifredo Sánchez Carrera、Jean-Luc Kerdelhué、Kevin J. Langenwalter、Neil Brown、Ralf Warmuth
DOI:10.1002/ejoc.200400578
日期:2005.6
absorption spectra. From the red shifts and from plots of the n-π*-excitation energy of the free diazirines against the solvent polarizability P, the inner-phase polarizability was estimated. P ranges from 0.39 to 0.58 and is larger than the polarizabilities of common organic solvents. A comparison of the activation parameters ΔH , TΔS , and ΔG for the diazirine decomposition in the innerphase with those in
The Elusive Benzocyclobutenylidene: A Combined Computational and Experimental Attempt
作者:Athanassios Nicolaides、Takeshi Matsushita、Kohichi Yonezawa、Shinji Sawai、Hideo Tomioka、Louise L. Stracener、Jonathan A. Hodges、Robert J. McMahon
DOI:10.1021/ja0039482
日期:2001.3.1
Ab initio and density functional theory calculations predict that benzocyclobutenylidene (1) has a singlet ground state in contrast to the parent phenylcarbene and many other simply substituted arylcarbenes. Calculations also predict that 1 should lie in a relatively deep potential well, while its tripler state is 14.5 kcal mol(-1) higher in energy. However,:attempts to observe 1 directly by photolysis of two different nitrogenous precursors were not successful. Irradiation of diazobenzocyclobutene (7) (lambda > 534 nm or lambda > 300 nm) or azibenzocycllobutene (10) (lambda > 328 nm) in Ar matrixes at 10 K leads to the formation of the strained cycloalkyne 7-methylenecyclohepta-3,5-dien-1-yne (3). C-13-Labeled 3 was also prepared in a similar manner. There is very good agreement between experimental IR spectra and computationally derived harmonic vibrational frequencies for 3 and [C-13]-3 and excellent agreement between observed and calculated isotopic shifts. Prolonged short-wavelength irradiation converts 3 into benzocyclobutadiene (5). Phenylacetylene (6) and benzocyclo- butadiene dimer (11) were identified as products arising from flash vacuum pyrolysis of diazirine 10 at 500 degreesC.
Benzocyclobutadienyl Anion: Formation and Energetics of an Antiaromatic Molecule
作者:Katherine M. Broadus、Steven R. Kass
DOI:10.1021/jo000709o
日期:2000.10.1
Benzocyclobutadienyl diazirine (2) was synthesized and reacted with hydroxide ion in a Fourier transform mass spectrometer to afford the conjugate base of benzocyclobutadiene (1a). Authentication of the ion structure was carried out by a derivatization experiment (i.e., la was converted to benzocyclobutenone enolate, which has previously been studied), and its reactivity was explored. Thermochemical