The electronic structure of carbon suboxide from ESCA and AB initio calculations

The ESCA spectrum of C₃O₂ excited by Mg K_α radiation, 1253.6 eV, has been obtained for both gaseous and solid samples. The chemical shifts of the C1s and O1s levels have been used to calculate the gross atomic charges. The valence region of the spectrum has been recorded and the ordering of the orbitals has been decided on the basis of an ab initio calculation and the intensities of the observed peaks. An unusually intense shake-up spectrum has also been observed and is discussed. The relative spacing of the valence peaks has been found to be different for the solid and gas.     

Perturbation calculation of oscillator strengths for the isoelectronic series of light atoms

Transition probabilities and oscillator strengths are calculated for the configurations 1s² 2sⁿ¹ and 1s² 2s^n1-1 2pⁿ²⁺¹, which are, respectively, of the form P=a/Z (1+/Z+) andf=/Z (1+/Z+). Numerical values are given fora, ,, and.     

Cd(II) determination in the presence of aqueous micellar solutions

The equilibrium constants and molar absorptivities for the fast formation of a 1:3 complex between cadmium(II) (Cd(II)) and dithizonate anion, in the presence of cationic and non-ionic surfactants, allowed a simple and fast spectrophotometric determination of total cadmium. Indeed, the molar absorptivities of the Cd(II)-dithizone (Dz) complex formed in the presence of the neutral Triton X-100 and cationic cetyltrimethylammonium bromide (CTAB) surfactants are almost twice the value observed in the standard method and the maxima of absorption are shifted by about 40 nm when compared with the standard method. Clearly, the use of neutral and cationic surfactants promotes a higher value of the molar absorptivities of the complex, resulting in an increase in the sensitivity of the method. Application of the method to the desorption of Cd(II) ions from clays is illustrated.     

Spherical molecularly imprinted polymers (SMIPs) via a novel precipitation polymerization in the controlled delivery of sulfasalazine

Spherical molecularly imprinted polymers (SMIPs) have been prepared via a novel precipitation polymerization using sulfasalazine (prodrug used in the diseases of the colon) as template. The sulfasalazine was incorporated into SMIPs and into a spherical non-imprinted polymer (control), and then the release rate of the bioactive agent at different pH values was evaluated. Considerable differences in the release characteristics between imprinted and non-imprinted polymers have been observed. This opens the possibility of the development of drug release systems capable of modulating the release of a specific molecule. Photomicrography of spherical molecularly imprinted polymers (SMIPs).     

Molecular beam investigation of hydrogen dissociation on Si(001) and Si(111) surfaces

The influence of molecular vibrations on the reaction dynamics of H2 on Si(001) as well as isotopic effects have been investigated by means of optical second-harmonic generation and molecular beam techniques. Enhanced dissociation of vibrationally excited H2 on Si(001)2 x 1 has been found corresponding to a reduction of the mean adsorption barrier to 390 meV and 180 meV for nu=1 and nu=2, respectively. The adsorption dynamics of the isotopes H2 and D2 show only small differences in the accessible range of beam energies between 50 meV and 350 meV. They are traced back to different degrees of vibrational excitation and do not point to an important influence of quantum tunneling in crossing the adsorption barrier. The sticking probability of H2 on the 7 x 7-reconstructed Si(111) surface was found to be activated both by H2 kinetic energy and surface temperature in a qualitatively similar fashion as H2/Si(001)2 x 1. Quantitatively, the overall sticking probabilities of H2 on the Si(111) surface are about one order of magnitude lower than on Si(001), the influence of surface temperature is generally stronger.     

ESR.-Messungen an Radikal-Anionen Trimethylsilyl-substituierter Hetero-π-Systeme

The ESR. spectra of the radical anions of trimethylsilyl-substituted derivatives of p-benzoquinone, phenylketone, diimine, p-benzoquinone-diimide, aniline and p-phenylenediamine are reported. In most cases the coupling constants of ²⁹Si isotopes in natural abundance have been measured. The comparison of the ESR. data for the radical anions of the trimethylsilyl derivatives with those for the radical anions of the corresponding parent hydrocarbons and/or alkyl-substituted compounds provide additional evidence for the overall electron withdrawing effect of the trimethylsilyl substituent (Si←C_π and Si←n_π delocalization).     

Über die Umsetzung von 2-Methyl-2,5-diphenyl-imidazolin-4-thion und 2-Methyl-2,5-diphenyl-4-chlor-2H-imidazol mit aliphatischen und aromatischen Aminen,Alkoholen und Phenolen

Zusammenfassung Aliphatische Amine bzw. Alkohole reagiren (in Gegenwart von PbO) mit 2-Methyl-2,5-diphenyl-imidazolin-4-thion (1) glatt zu 4-Alkylamino-2H-imidazolen (2 a-f, 7) bzw. 4-Alkoxy-2H-imidazolen (9 a-g). Die Darstellung von 4-Arylamino-2H-imidazolen (4 a-j) bzw. 4-Aroxy-2H-imidazolen (10 a-t) gelingt in guten Ausbeuten durch Umsetzung von 2-Methyl-2,5-diphenyl-4-chlor-2H-imidazol (3) mit aromatischen Aminen in siedenden Lösungsmitteln (Petroläther, Aceton) bzw. mit Phenolen in siedendem Aceton in Gegenwart von HCl-Acceptoren (K₂CO₃, Dabco). Die Umsetzung von3 mit Anthranilsäure liefert in 83proz. Ausbeute 1-Methyl-1,3-diphenyl-1H, 9H-imidazo[5,1-b]chinazolin-9-on (6). Aus3 und Thiophenol erhält man glatt 2-Methyl-2,5-diphenyl-4-phenylthio-2H-imidazol (11).

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On the reaction of 2-Methyl-2,5-diphenyl-imidazoline-4-thione and 2-Methyl-2,5-diphenyl-4-chloro-2H-imidazole with aliphatic and aromatic amines, alcohols and phenols (joint action of elemental sulfur and gaseous ammonia upon ketones, LXXVI

Aliphatic amines and alcohols (in the presence of PbO) easily react with 2-methyl-2.5-diphenyl-imidazoline-4-thione (1) to 4-alkylamino-2H-imidazoles (2 a-f, 7) and 4-alkoxy-2H-imidazoles (9 a-g), resp. 4-arylamino-2H-imidazoles (4 a-j) are prepared in good yields by the reaction of 2-methyl-2.5-diphenyl-4-chloro-2H-imidazole (3) with aromatic amines under reflux in light naphtha or acetone; in the same manner 4-aroxy-2H-imidazoles (10 a-t) are obtained from3 and phenols in boiling acetone in the presence of HCl-acceptors (K₂CO₃, Dabco). Reaction of3 with anthranilic acid leads to1-methyl-1.3-diphenyl-1H.9H-imidazo[5.1-b]chinazoline-9-one (6) in 83% yield. By reaction of thiophenol with3 2-methyl-2.5-diphenyl-4-phenylthio-2H-imidazole (11) is easily obtained.

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Herrn Prof. Dipl.-Ing., Dr. techn., Dr. e. h.Otto Kratky zum 70. Geburtstag herzlichst gewidmet.

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Teil der DiplomarbeitJ. Gräber, Techn. Hochschule Aachen, 1970.

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Teil der DiplomarbeitU. Lames, Techn. Hochschule Aachen, 1971.     

Tribochemische und thermische Umwandlungen von LnTa3O9 (Ln = Pr,Nd) – röntgenographische und elektronenmikroskopische Untersuchungen

Tribochemical and Thermal Transitions of LnTa₃O₉ (Ln = Pr, Nd) — X-ray and Electron Microscopic Investigations Upon grinding crystals of M1? LnTa₃O₉ (Ln = Pr, Nd) [3] undergo a tribochemical phase transition. This leads to a new modifikation M2? LnTa₃O₉ with a significant higher density. We tried to find out more about the structure with high resolution electron microscopic investigations. According to electron diffraction and powder patterns the lattice parameters are (CuKα₁, λ = 1,54051 Å): M2? PrTa₃O₉: a = 6.2545(7) Å, b = 7.6736(7) Å, c = 6.5316(8) Å, β = 93.93(9)°; M2? NdTa₃O₉: a = 6.2552(5) Å, b = 7.6598(7) Å, c = 6.5103(4) Å, β = 94.096(7)°; (Z = 2). Using the intensities of powder patterns two structure models were calculated (space group P2₁/m, P2/m; R < 20%, heavy metal positions only). A through focus series of high resolution images was in better agreement with the first model (space group P2₁/m). Both models show a remarkable similarity to the structure of M? CeTa₃O₉ [4]. A thermal phase transition leads to M? PrTa₃O₉ and M? NdTa₃O₉ which are both isostructural to M? CeTa₃O₉.     

Microcalorimetric studies of slag alkaline binders

Calorimetric measurements were carried out on the hydration of slag activated by sodium hydroxide, sodium carbonate and water glass at 60 °C. The results can be correlated with the mechanical properties of the cured cements. The studies confirmed the applicability of calorimetry in the testing of activators used in concrete technology.

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Zusammenfassung Die Hydratation von Schlacke bei 60 °C und Aktivierung mit Natriumhydroxid, Natriumcarbonat oder Wasserglas wurde durch kalorimetrische Messungen verfolgt. Die Ergebnisse lassen sich mit den mechanischen Eigenschaften der erhärteten Zemente korrelieren. Die Untersuchungen bestätigen die Brauchbarkeit der kalorimetrischen Methode zum Testen von Aktivatoren in der Betontechnologie.

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, 60° , . . , - .