Oxidation metallorganischer verbindungen : I. Zur oxidation isomerer diibutylaluminium-n-hexanolate

Oxidation of isomeric diisobutylaluminium-n-hexenolates with oxygen yields after subsequent acetolysis besides the expected hexenol acetates also hexanetriol triacetates. Their formation is explained by intramolecular epoxidation with alkylalkoxyaluminium peroxides formed during the oxidation.     

Intermediate mass fragments emitted in the reaction Ag+14N at 100, 160 and 250 MeV bombarding energy

The fragments produced in the reaction between a ¹⁴N beam of various energies and a natural Ag target have been studied. The atomic numbers of the fragments have been identified up to Z = 17 by means of a E-ΔE counter telescope. The cross sections, the kinetic energy distributions as well as the angular distributions have been measured for each atomic number. The kinetic energy distributions show two components: a high-energy component (quasi-elastic), prevailing at angles close to the grazing angles and for atomic numbers close to Z = 7, and a low-energy component (relaxed), at energies close to the Coulomb repulsion energy, present at all angles and for all the Z. A detailed study of the relaxed components of the kinetic energy seems to account for both them means and the widths of these distributions on a purely statistical basis. The cross sections of the relaxed components appear to be quite large at low Z and to decrease rapidly to a fairly constant value in the region of 10 ≦ Z ≦ 17. A marked even-odd alternation in the cross sections is observed. The angular distributions are strongly forward peaked for Z < 7. For Z > 7 the forward peaking decreases rapidly until, for Z > 13, the limiting form 1/sinθ is attained. Evidence for the existence of a diffusion process along the mass asymmetry coordinate is discussed.     

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Characterization of thin superconducting YBACuO-films by Raman-spectroscopy

We have investigated thin sputtered films of the highT _c material YBa₂Cu₃O₇ by means of Raman spectroscopy at different stages of the preparation process. We find that the films are amorphous after sputtering. The Raman spectra indicate that random polycrystalline layers, as well as crystalline layers with preferred orientation, are obtained by an additional thermal treatment.     

Characterization,by inverse gas chromatography,of the surface properties of calcium carbonate before and after treatment with stearic acid

Summary The interaction of n-alkanes with stearyl chains chemically fixed on the surface of calcite particles is investigated using inverse gas chromatography. Free enthalpy, enthalpy, entropy of adsorption and dispersive component of the surface free energy are determined. Untreated and stearic acid treated calcites have comparable affinities for the alkanes. However, the differences in adsorption entropies point to different interaction mechanisms: gas-solid adsorption for the untreated calcite and gasliquid interactions for the modified sample. Furthermore, for long chains probes, having more than 8 carbon atoms, the loss in entropy is smaller than for shorter chains. Possibly, long chains are only partially inserted in between the stearyl grafts, thus keeping a higher degree of freedom.     

2H, 13C shift correlation as an analytical tool for the study of deuteriated carbon compounds

A chemical shift correlation experiment for ²H, ¹³C spin systems is described. Applications to the analysis of deuteriated carbon compounds are discussed and advantages over existing methods are pointed out.     

Neue m-Phenylen-bis-disubstituierte Phosphane

New m-Phenylene-bis-disubstituted Phosphanes New m-phenylen-bis-disubstituted phosphanes are described. The crystal structure of a new manganese-phosphane complex 4 is reported.     

Heat and mass transport in the photoacoustic effect on liquids

The temperature oscillation accompanying the photoacoustic effect generates a periodic variation of the vapor pressure of a liquid. The propagation of the oscillating concentration of the vapor in the inert cell gas (air) is described by a mass diffusion wave on which a convective motion of the gas is superposed. The diffusion wave characterized by the diffusion coefficient of the cell gas alone can be measured by the Mirage effect, whereas a microphone detects the total mass flux including the convective flux, which increases with temperature. On approaching the boiling temperature, the convective flow will govern the oscillating transport of mass. The photoacoustic signal is determined directly from the flux of heat and mass at the boundary between liquid and gas using the Gauss' divergence theorem. We have found that the temperature behaviour of the amplitude and phase angle of the photoacoustic signal depends on the length of the gas column in the cell. The contribution of thermal expansion to the photoacoustic signal is considered using the composite piston model. The results of the calculations agree fairly well with the experimental data.