Cationic polymerization of isobutene initiated by stannic chloride and phenols: Polymer endgroup studies

Low molecular weight polymers of isobutene produced with stannic chloride as catalyst and phenols as cocatalysts have been subjected to ultraviolet and NMR analysis. A high proportion of the endgroups are derived from the phenol cocatalyst when the concentration of free phenol in the reaction mixture at ?78.5°C is fairly large. At low concentrations of free phenol, termination to give vinylidene endgroups becomes more significant. The results lend support to the suggestion that an important mode of termination in this polymerization system involves the reaction between a growing carbonium ion and the phenol cocatalyst.     

Über die Bestimmung der Richtung von Übergangsmomenten in länglichen Molekülen aus Messungen des IR-Dichroismus, 3. Mitt.:

Zusammenfassung Es wurde an 4-Dimethylaminoazobenzol der Dichroismus der N=N-Valenzbande sowie an -Poly--Benzyl-L-glutamat der Dichroismus der NH-Valenzbande, der Amid I-Bande und der Amid II-Bande gemessen. Aus den Meßwerten konnten mit den in der ersten und zweiten Mitteilung¹ abgeleiteten Beziehungen die Richtungen der Übergangsmomente berechnet werden. Die Ergebnisse zeigen eine ausgezeichnete Übereinstimmung mit den theoret. Werten.

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Determination of the direction of transition moments on oblong molecules by measurement of infrared dichroism, III

The dichroism of the -N=N band in p-dimethyl-amino-azobenzene and of the -NH band, the amid I band and the amid II band in -poly--benzyl-L-glutamate has been measured. By the relations derived in the first and second communication¹ directions of the transition moments could be calculated. The results are in excellent agreement with theoretical values.

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Mit 2 Abbildungen     

On the origin of electron stimulated desorption of H+ from metal surface

The emission of hydrogen ESD ions from polycrystalline Nb is studied experimentally. The results demonstrate clearly that no ESD emission of H⁺ occurs from a pure H adsorbate. However, adsorption of H₂O, present as an impurity in H₂, and H₂ adsorption on Nb preceded by O adsorption, produce strong H⁺ ESD emission. It is shown that Auger ionization of O can account for the increased H⁺ yield and it is postulated that similar effects also occur on other metal surfaces.     

Eine spektralphotometrische Simultanbestimmung von H?moglobin und Rivanol in L?sung

Ohne Zusammenfassung     

57Fe Mössbauer studies of nickel hydride

Nickel loaded with hydrogen electrolytically or under high pressure was studied by⁵⁷Fe Mössbauer spectroscopy on dilute substitutional iron solutes. Experiments in external magnetic fields at 4.2 K show that Fe species in nickel hydride have magnetic moments between about 4.7 and 2.5 μ_B and saturation hyperfine fields between 24 and 17 T, depending on the number of nearest hydrogen neighbours. By quenching hydride samples from ambient to liquid nitrogen temperature, non-equilibrium hydrogen distributions in the vicinity of the iron can be frozen in. They relax towards equilibrium between 130 and 150 K within hours, permitting information on hydrogen jump rates to be obtained.     

Strukturaufklärung eines Dimethylfulven-Trimeren. Hinweis auf eine [6 + 4]-Cycloaddition von 6, 6-Dimethylfulven

Structure Elucidation of a Dimethylfulvene-trimer. Evidence for a [6+ 4]-Dimerization of 6, 6-Dimethylfulvene Thermal reaction of pure 6, 6-dimethylfulvene ( 1c ) at 60° gives an oligomeric mixture consisting mainly of fulvene-trimers. The structure of the main product 3c is partially elucidated by ¹H-NMR. investigations at 400 MHz and definitely confirmed by X-ray analysis. The formation of 3c is explained in terms of a [6+4] dimerization, followed by a 1, 5-proton-shift and a final Diels-Alder reaction.     

Chloracylierung und Bromacylierung von Carbonylverbindungen. III. Lage des Gleichgewichts

Chloroacylation and Bromoacylation of Carbonyl Compounds III. Reactant/Product Equilibria Aliphatic, α, β-unsaturated and aromatic aldehydes 1 as well as aliphatic ketones react with acyl halides 2 to α-haloalkyl esters 3 . In the presence of Lewis acids there is an equilibrium between reactants and product. The position of the equilibrium depends on the nature of the carbonyl compound as well as that of the acyl halide: The products 3 are favoured in the case of aldehydes, cyclobutanone and cyclohexanone, and the equilibrium constant increases in the series F < Cl < Br < I. Low reaction temperature, nonpolar solvents as well as high reactant concentrations favour the product 3 .