Spektroskopische Untersuchungen an Siliciumverbindungen. XXXI. Schwingungsverhalten von p-substituierten N,N-Bistrimethylsilylanilinen

The following p-substituted N,N-bis-trimethlsilyl anilines p-X? C₆H₄? N[Si(CH₃)₃]₂ are prepared by silylation of free amines: X = H, CH₃, C₂H₅, CH₃O, CH₃CO, F, Cl, Br, J, CN, C₆H_S, (CH₃)₃SiO, and [(CH₃)₃Si]₂N, and the isotopic derivatives C₆H₅? ¹⁵N[Si(CH₃)₃]₂ and C₆D₅N[Si(CH₃)₃]₂. The vibrational spectra are reported and assigned. The molecular symmetry of p-[(CH₃)₃Si]₂N? C₆H₄? N[Si(CH₃)₃]₂ is determined. The influence of the mass of the substituents X on the positions of the ν_sSiNSi vibrational frequencies is discussed.     

Lösungsmittel-, Viskositäts-, Säure- und Substituenteneinflüsse auf die Photoisomerisierung und Relaxation symmetrischer Triazacarbocyanine bei 283 bis 323 K

Influence of Solvents, Viscosity, Acid, and Substituents on the Photoisomerization and the Relaxation of Symmetrical Triazacarbocyanine Dyes at 283 to 323 K Photobleaching and the reverse dark reaction of seven symmetrical triazacarbocyanine dyes with different heterocycles were studied dependent on solvent effects (protic and aprotic solvents), on effects of viscosity (glycerol/EtOH mixtures), and on effects of added acid. No effects of dissolved O₂ or added I₂ has been observed. Kinetic data (ΔH^≠, ΔS^≠, and ΔG) of the reverse reaction are given. The effect of the substituents has been studied on two series of substituted triazacarbocyanine dyes. The mechanism of the reverse reaction is discussed.     

Spektroskopische und röntgenographische Untersuchungen an Dichlormethyl-Quecksilberverbindungen

Spectroscopic and X-Ray Structural Investigations on Dichloromethyl Mercury Compounds Bis(dichloromethyl)mercury, Hg(CHCl₂)₂, and mixed alkyl compounds RHgCHCl₂ (with R = CH₃, C₂H₅) have been synthesized by known methods from CH₂Cl₂, lithium butanide and HgCl₂, CH₃HgCl or C₂H₅HgCl, respectively. The ¹H-, ¹³C-NMR as well as the IR and Raman spectra of the liquid alkyls RHgCHCl₂ and the high melting Hg(CHCl₂)₂ have been measured and assigned. According to the X-ray structure determination Hg(CHCl₂)₂ crystallizes in the monoclinic space group P2₁/c with 4 non-symmetric molecules per unit cell (R = 0.046).     

Spektroskopische Untersuchungen an Schwefelverbindungen. VII. 1H- und 13C-NMR-spektroskopische Untersuchungen an Alkansulfinsäurechloriden und Chloroschwefligsäurealkylestern

Spectroscopic Studies on Sulphur Compounds. VII. ¹H- and ¹³C-NMR Spectroscopic Investigations of Sulphinic Acid Chlorides and Chloro-sulphurous Acid Alkylesters The temperature dependent ¹H- and ¹³C-n.m.r. spectra of the sulphinic acid chlorides R—S(O)Cl and of the chloro-sulphurous acid alkylesters RO—S(O)Cl with R = CH₃CH₂- and (CH₃)₂CH- have been measured. The differing behaviour of both nuclei is discussed in terms of inversion at the chiral sulphur atom.     

Spektroskopische und röntgenographische Untersuchungen an methylenverbrückten Organoantimonverbindungen

Spectroscopic and X-Ray Structure Investigations on Methylene Bridged Organoantimony Compounds The vibrational spectra of (Me₂Sb)₂CH₂ and of the halogen derivatives (Me₂Cl₂Sb)₂CH₂ and (Me₂Br₂Sb)₂CH₂ (Me = CH₃) have been measured and discussed. The i.r. and Raman data for liquid bis(dimethylstibino)methane are consistent with a mixture of two rotamers of C_s and C_2v symmetry, respectively. For the halogen compounds only one form is spectroscopically proved. The X-ray structure determination of (Me₂Cl₂Sb)₂CH₂ · CH₂Cl₂ shows the monoclinic space group P2₁/n with a = 968.2; b = 1746.8; c = 982.2 pm and β = 91.95°. The structure was refined to an R-value of 0.038.     

Untersuchungen an Metallkatalysatoren. XXXII. Zur Legierungsbildung und Dispersität von Nickel-Rhenium-Katalysatoren

Investigations on Metal Catalysts. XXXII. On Alloying and Dispersion of Nickel-Rhenium Catalysts Unsupported Ni? Re catalysts were prepared by reduction of mixtures from NiO and NH₄ReO₄ at 400°C with hydrogen (1^st series), followed by a heat treatment at 650°C in flowing hydrogen (2^nd series). The bimetallic powders were characterized by DTA investigations, X-ray measurements, N₂ adsorption, and CO chemisorption. The degree of alloying and the changes in dispersion as a result of adding a second metal to a basic one is discussed.     

Protonenresonanzuntersuchungen an Aminoboranen—II: Einflüsse von para-Phenylsubstituenten auf die Rotationsbarriere um die N?B-Bindung

The electronic influence of substituents on the free enthalpy of rotation around the N? B bond in aminoboranes was investigated in two series of compounds: (a) (CH₃)₂N?BCl (phenyl-p-X), containing the para-phenyl substituent at the boron atom, and (b) (p-X-phenyl)CH₃N?B(CH₃)₂, containing the para-phenyl substituent at the nitrogen atom of the N? B linkage (X = ? NR₂, ? OCH₃, ? C(CH₃)₃, ? Si(CH₃)₃, ? H, ? F, ? Cl, ? Br, ? I, ? CF₃ and ? NO₂). By comparing the rotational barriers in corresponding compounds of both series, a reverse effect of the substituents could be observed. Electron-withdrawing substituents in the para position of the phenyl ring increase the ΔG_c^≠ if the phenyl group is attached to the boron atom; on the other hand, a lower ΔG_c^≠ is observed if the phenyl ring is bonded to the nitrogen atom of the N? B system. Substitution of the phenyl ring with electron-donating substituents in the paraposition exerts the opposite effect. Within each series of compounds, the differences of ΔG_c^≠ values [δ(ΔG_c^≠) = ΔG_c^≠ (X) ? ΔG_c^≠ (X = H)] between substituted and unsubstituted compounds can be explained in terms of inductive and mesomeric effects of the ring substituents and can be correlated with the Hammett σ constant of each substituent. A comparison of the slopes of the plotted lines shows that the influence of the ring substituents is more pronounced in compounds with N-phenyl-p-X than in those with B-phenyl-p-X.     

Sterische Einflüsse auf die Dissoziationskonstanten von acyclischen,mono- und bicyclischen Carbonsäuren

Steric effects on the dissociation constants of acyclic, mono- and bicyclic carboxylic acids Apparent pK values for the series of acyclic, mono- and bicyclic acids 1–14 have been measured in 50% (W/W) ethanol (see the Table). The dissociation constants of these acids decrease as the access of the solvent to the carboxylate group is hindered by the rest of the molecule. These results emphasize the importance of solvation in determining acid strength. New or improved syntheses of several of the acids investigated are reported.     

Untersuchungen an Metallkatalysatoren. XXVII. Zum Einfluß verschiedener Träger auf die Dispersität von Nickel

Investigations on Metal Catalysts. XXVII. On the Influence of Several Carriers on the Dispersion of Nickel Nickel supported catalysts (carrier: η-, ?-, α-Al₂O₃, TiO₂) were characterized by chemically determined degree of reduction, CO chemisorption, magnetic susceptibility measurements and FMR. The influence of interaction between carrier and active component in the unreduced state on the size and number of Ni crystallites is discussed.     

Untersuchungen über die elektrolytische Uranabscheidung auf Metallen. II

Zusammenfassung Die erstmalige Verwendung von Ammoniumfluorid als Elektrolyt bei der Herstellung dünner Uranoxidschichten auf Stahl, Aluminium und anderen Metallen wird beschrieben. Die Untersuchungen zeigen die Abhängigkeit der Uranabscheidung von der Elektrolytkonzentration, der Acidität und dem Volumen. Der Zeitaufwand hängt von der Ammoniumfluoridkonzentration ab, kann jedoch durch Rühren mittels der Anode selbst stark herabgesetzt werden. Die Abscheidung des Urans gelingt quantitativ bis zu Schichtdicken von etwa 0,5 mg U/cm², doch lassen sich auch Präparate bis zu 1 mg U/cm² und 6 cm² Fläche herstellen.

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Summary The first use of ammonium fluoride as electrolyte in the production of thin layers of uranium oxide on steel, aluminium and other metals is described. Studies reveal the dependence of the deposition of the uranium on the electrolyte concentration, the acidity, and the volume. The time required depends on the concentration of ammonium fluoride but can be greatly reduced by stirring by means of the anode itself. The deposition of the uranium is quantitative up to layer thicknesses in the neighborhood of 0.5 mg U/cm², but preparations up to 1 mg U/cm² and 6 cm² can be prepared.

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Résumé On décrit pour la première fois l'emploi du fluorure d'ammonium comme électrolyte dans la préparation de couches minces d'oxydes d'uranium sur l'acier, l'aluminium et d'autres métaux. Les expériences montrent que le dépôt d'uranium dépend de la concentration de l'électrolyte, de l'acidité et du volume. La durée nécessaire varie avec la concentration en fluorure d'ammonium; elle peut être fortement abaissée en agitant l'anode elle-même. Le dépôt d'uranium s'effectue quantitativement pour les couches dont l'épaisseur va jusqu'à 0,5 mg U/cm² environ; on peut toutefois réaliser aussi des préparations allant jusqu'à 1 mg U/cm² et 6 cm² de surface.

     

Untersuchungen an oxidischen Katalysatoren. XXXIX. Der Einfluß acider Träger auf die katalytische Wirksamkeit von Metallen

Studies on Oxide Catalysts. XXXIX. Influence of Acidic Carriers on the Catalytic Effect of Metals The catalytic behaviour of modified zeolite catalysts containing metal in the isomerization of n-hexane as well as in the dehydrogenation of cyclohexane and in the hydrogenolysis of ethane shows that the catalytic action of the metal can be continuously and reversibly varied by modifying the carrier acidity. From the concept of an electronic interaction between metal and (acid) carrier conclusions can be derived for a directed modification of the catalytic properties of metal/carrier catalysts.     

Untersuchungen an Systemen aus Salzen und gemischten Lösungsmitteln. XXXII. Zur Solvatation von Kationen (Li+, Mg2+, Al3+) in N,N-Dimethylformamid-Wasser-Gemischen. Ramanspektroskopische Untersuchungen an konzentrierten Elektrolytlösungen

Studies on Systems of Salts and Mixed Solvents. XXXII. On the Solvation of Cations (Li⁺Inhaltsübersicht., Mg²⁺, Al³⁺) in N, N-Dimethlformamide-Water Mixtures. (Raman Spectroscopic Investigations of Concentrated Electrolyte Solutions) In concentrated electrolyte solutions mixed ligand complexes with changing composition exist. Dimethylformamide substitute water molecules bonded in aquo complexes because of its higher donocity. It is reported about the raman spectroscopic detectable cation-DMF interactions in concentrated solutions. The interpretation of the vibrational spectrum in the OCN-region permits the quantitative determination of DMF molecules coordinated in the first coordination shell of cations regarding the scattering cross section. The behaviour of v_CO illustrates that the interactions between cations and the lone pairs of the carbonyl oxygen are not purely electrostatic in nature.     

Untersuchungen an katalytisch aktiven Oberflächenverbindungen. XI. Einfluß der Topologie der Silanolgruppen auf die Bildung von Vanadiumoxidclustern auf SiO2-Oberflächen

Studies on Catalytically Active Surface Compounds. XI. Influence of the Topology of Silanol Groups on the Formation of Vanadium Oxide Clusters on SiO₂ Surfaces Interaction of VOCl₃ dissolved in CCl₄ with silanol groups of Aerosil gives rise to reaction products, the Cl/V-ratio of which depends on thermal pretreatment of Aerosil and the amount of the vanadium fixed on the surface. Geometrically different arrangements of the silanol groups (centers) show kinetically differing behaviour, thus giving the possibility to establish a mathematic model for the interpretation of experimental data. Quantitative estimation of the population with silanol groups depending on the annealing temperature is achieved and correlated with the existence of two vanadium oxide surface species which differ with respect to their catalytic activity.     

Untersuchungen an Chitin. 2. Mitt. Einflu? der Deacetylierung auf die L?slichkeit

Ohne Zusammenfassung