Induction asymetrique—II: Determination des configurations relatives de δ-amino β-hydroxyesters diastereoisomeres,obtenus par la reaction de reformatsky

Addition of Reformatsky reagents (R₁-CHZnBr-CO₂R) to three β-aminoketones, yields mixtures of threo and erythro diastereomeric aminohydroxyesters. The relative configurations of the first members of each series (R₁CH₃), were determined by chemical correlation. Those of higher homologues (R₁C₂H₅, iC₃H₇,tC₄H₉) are assigned by a study of their NMR spectra.     

Synthesis and Characterization of Monodisperse Spherical Zirconia Particles

Monodisperse zirconia spherical particles are prepared by hydrolysis of zirconium propoxide in 2-methoxyethanol in presence of decanoic acid as a shape stabilizer. The powder is analyzed by computer image analysis on TEM micrographs, TG-DSC, FTIR, X-ray diffraction and nitrogen adsorption isotherms. A competition phenomenon between aggregation and individual growth of the particles during precipitation is deduced from the observations.     

Geometry of equilibrium configurations in the Ising model

We derive microscopically precise identities for the geometry of small clusters in the equilibrium states of the two-dimensional Ising model with emphasis on near-critical phenomena.     

Synthesis of difluoromethylthio imidazole from methylthio imidazole

Demethylation of methylthio imidazole 1 via a Pummerer rearrangement onto the corresponding sulfoxide 2 afforded imidazole thiol 4 which was then difluoromethylated with the sodium chlorodifluoroacetate/NaI system in 71% overall yield.     

Styrene cis—trans photoisomerisation treated through a Heisenberg non-empirical hamiltonian

Using a recently proposed non-empirical Heisenberg hamiltonian, the ground and excited covalent surfaces of the styrene molecule are calculated as functions of the external double-bond twisting angle θ, including full bond-length optimisation. The lowest excited singlet surface exhibits a barrier at 0 ?~ 45° resulting from a weakly avoided crossing of two neutral diabatic surfaces. The isomerisation should proceed from the twisted funnel. This model and the calculated transition energies are in good agreement with experiment.