Quantum chemical interpretation of 13C NMR spectra of adsorbed molecules

In order to assist the interpretation of carbon-13 NMR spectra for molecules sorbed on solid surfaces, a theoretical analysis of resonance shifts was performed which were measured for simple alkenes and arenes in zeolites of type X and Y and on silica gel surfaces. Quantum chemical computations for simple models of adsorption complexes on the basis of CNDO and PCILO methods were combined with resonance shift calculations by means of the Ramsey theory and by employing an empirical formula to find out the most probable structures for the adsorption complexes.     

Kinetic Description of the Stationary Band-Like Weakly Turbulent Beam Discharge Plasma in Hydrogen. I. Basic Equations — Numerical Approach — Ionization and Dissociation Budget

On the basis of the electron Boltzmann equation and of the balances for the charge carriers (e, H⁺, H₂⁺, H₃⁺), the H-atoms and the metastable H(2s)-atoms for the H/H₂-mixture the behaviour of the weakly turbulent, band-like electron-beam discharge plasma in hydrogen has been calculated taking into account the main collision and transport processes. In dependence of the normalized discharge length, the life time of the neutral particles in the band-like plasma and the electron beam generated turbulence energy density the ionization and dissociation budget and in particular the most important electron-heavy particle collision rates, which appear in the balance equation system, are investigated in the present part of our paper. In a second part the results related to the budget of the ions and the metastable atomic state will be reported and an analysis of the main processes in the balances will be made.     

Microscopic model of NaNO2 in the paraelectric phase

Starting from a sterical hindrance potential for the motion of the NO₂-molecular group in the deformable cage of neighbouring Na-ions, we derive a microscopic model for the NaNO₂ crystal in the paraelectric phase. The dynamical variables are the translational displacements of both the NO₂-groups and the Na-ions, and the reorientations of the NO₂-groups. Reorientations are described by means of symmetry adapted functions. From a numerical study of the model, we conclude that reorientations of the NO₂-groups take place essentially through rotations about the crystallographicc-axis. The model explains why optical experiments have led to the incorrect conclusion of reorientations about thea-axis. By studying the symmetry properties of the bilinear coupling of translations and rotations, we separate optical and acoustical displacements. Only the former couple to the order parameter in the long wavelength limit. Therefore there is no acoustical soft mode at the ferroelectric phase transitions. The bilinear coupling leads to an effective lattice mediated interaction among reorienting NO₂-groups.     

507—Electron transport through human epithelial amniotic membrane in vitro: Comparative study with artificial membranes (bilayer and millipore filters)

The transfer of solutes and water across the amniotic membrane, in vivo, is controlled by hydraulic, osmotic and electrochemical factors. In this study the electrochemical component is specified in vitro, and the mechanism of ion transport across the amnion is characterized by comparison with artificial membranes (bilayers and Teflon millipore filters). The electrochemical study shows that the amniotic conductance depends on time and salt concentration; the cationic transference number is comprised between 0.75 and 0.85; the electro-osmotic potentials are negative; the I(V) curves are linear; the activation conductance energy ranges between 4 and 8 kcal degree^?1 mole^?1 and the cation selectivity sequence is: RbCsK>Na>Li. The pharmacological agents (ouabain, amiloride, dinitrophenol) decrease gNa. These results suggest: (1) that the amnion has fixed neutral sites in external epithelial cell membranes and on intercellular channels with, under certain conditions, negative sites in greater number than positive sites; (2) that the amnion is comparable to negative artificial membranes; (3) that the paracellular pathway is more important than the transcellular pathway; (4) that there are specific sites on the external membranes and in intercellular channels.     

Synthèse et Propriétés d'Alkylidénehydrazono-2 Méthyl-3 Dihydro-2,3 Benzothiazoles

The synthesis and the spectral properties of 2-alkylidenehydrazono-3-methyl-2,3-dihydrobenzothiazoles are reported. In the mass spectra of each of these compounds, the main fragmentation implies the breaking of the ?N? -N?bond of the azine.     

Les équations de Hua d'un domaine borné symétrique du type tube

Sans résumé     

Catalyseurs Ziegler-Natta supportés sur MgCl2 pour la polymérisation du propène. I. Etude de la réaction entre le triéthylaluminium et le benzoate d'ethyle

In this article we describe a study of the reaction between triethylaluminium (TEA) and ethylbenzoate (BE) in a heptane solution by Fourier transform, infrared (IR), and ultraviolet (UV) spectroscopy. These compounds were chosen as a model of the cocatalytic solution used with a Ziegler-Natta catalyst supported on MgCl₂ for the stereospecific polymerization of propene. In the polymerization concentration range a 2 TEA:1 BE yellow complex was added to the solution and no free BE could be detected at a AI/BE molar ratio above 2: the solution contained only free and complexed TEA. The complex decomposed spontaneously to a colorless aluminium alcoholate. The rate of decomposition remained slow at room temperature and the reaction was enhanced by heating or by a high AI/BE ratio or high AI concentration. The decomposition was inhibited in the presence of an olefin.     

Synthesis of new norbornenones with the aminoester group methyl bicyclo [2-2-1] hept 5-ene 7-one 1-amino 2-carboxylates

Amino norbornenonecarboxylates were synthesized from methyl acrylate and amino butadienecarboxylates. This result is equivalent of amino cyclopentadienones Diels-Alder reaction. Amino butadienecarboxylates were prepared by prototropic transposition of the β-allenic aminoesters.