Generalized nuclearity conditions and the split property in quantum field theory

Generalized nuclearity conditions that are applicable in arbitrary superselection sectors of a quantum field theory and to theories with a maximal temperature are discussed. They are shown to imply the (distal) split property and to impose specific restrictions on the spectral properties of modular operators associated with local algebras and vectors of compact energy support.     

Electronic Absorption Spectra of Planar,Conjugated Biradicals in the Lowest Triplet State

The semiempirical PPP-SCF-SCI method has been adapted to even-electron, open-shell π-systems by performing the SCF calculation on the lowest triplet configuration and choosing a limited set of single electronic excitations from the latter for configuration interaction. The basic approximations and parameters of the standard PPP model were retained. The results were compared with experimental triplet-triplet absorption spectra of aromatic hydrocarbons and with more elaborate calculations available for selected systems. The reliability of the model was found to be comparable to its well-known performance in predicting the absorption spectra of closed-shell π-systems and of conjugated radicals. Triplet-state absorption spectra for various planar, conjugated biradicals were calculated and, where possible, compared with experimental data.     

Complete enantiospecificity in the highly regioselective and stereoselective photo- and thermal rearrangements of some homoconjugated ketones

The oxa-di-π-methane (ODPM) photorearrangement of 2-(carbomethoxy)spiro [5.5]undeca-1,3-diene-7-one ($\text{1}$d) to $\text{2}$d and the latter's thermal rearrangement to $\text{3}$d were shown to be not only fully regio-and stereoselective but also to occur with complete enantiospecificity. An additional example, the 2-hydroxymethyl derivative ($\text{1}$f) was also studied and the two systems were chemically correlated.     

Real parts of πN forward amplitudes at high energies

Since predictions from high energy cross sections alone are not reliable, real parts above 10 GeV/c have been calculated from dispersion relations, using the most recent data and a simplified method.     

Novel bromination reagents · hexabromocyclopentadiene: bromination of activated saturated sites

Hexabromocyclopentadiene (HBC) readily brominates α-keto and benzylic sites, apparently by bromonium ion transfer.     

Conjugative Stabilization in an “Antiaromatic” System: The Conformational Mobility of 1,5-Bisdehydro[12]annulene

The isodynamical interconversion between the quasiplanar equilibrium conformers 1b and 1c of 1,5-bisdehydro[12]annulene requires a free energy of activation ΔG^# = 4.5 ± 0.2 kcal/mol (120 K) which was determined by line shape analysis of its temperature-dependent NMR. spectrum. Force field calculations indicate that this barrier reflects the energy needed to disrupt the cyclic π-conjugation in going to the nonplanar transition state 1a .