Einige Aspekte der Quantitativen Röntgenemissionsanalyse Leichter Elemente bei Anregung Mit Schweren Teilchen

The aim of the paper is the simplification of calibration procedures in the investigation of multi-element-systems by calculating calibration curves. This requires, as well as taking into account the measuring geometry and the detector properties, above all the calculation of the number of the characteristic X-rays emitted by the sample per incident particle. For the calculation of the thick target yield a computer programme has been developed which makes possible a simple exchange of subroutines describing the stopping power of the sample, the cross-section of K-shell ionization, the fluorescence yield and the matrix absorption for the resulting K-X-rays of the elements contained in the sample. The agreement between experiment and calculation is discussed, when various approximations for the functions mentioned are used, as well as the possible influence of the grain size and surface roughness of the samples on the measurements, on which the calculations are based.      

Strukturelle Abwandlungen anN-Acetylneuraminsäure, 3

From methyl-5-acetylamino-7,8-anhydro-4,9-O-bis-(t-butyldimethylsilyl)-3,5-dideoxy--D-glycero-D-galacto-2-nonulopyranosidonic acid methylester (1) the derivatives1 a and1 b were obtained by removing the 9-O-(t-butyldimethylsilyl)group withBu ₄NF, followed by acetylation. Treatment of1 b with 80% acetic acid and acetanhydride/pyridine yields the 8-epi-N-acetylneuraminic acid derivative2 a and the 7-epi-N-acetylneuraminic acid derivative3 a in a ratio of 3:1 (Scheme 1). The structure elucidation of2 b was achieved by converting2 b via the 4,9-bis-O-(tBDMSi)-8-O-tosyl-derivative2 d into the epoxide1 (Scheme 2). Using the same sequence the epoxides4 and5 were transformed into theN-acetylneuraminic acid derivative6 a and the 7,8-bis-epi-N-acetylneuraminic acid derivative7 a (Scheme 3). After treatment with sodium hydroxide and 0.025m HCl and Dowex 50 H⁺ the 8-epi-, 7-epi- and 7,8-bis-epi-N-acetylneuraminic acids2,3, and7 were obtained. These three compounds were tested withCMP-N-acetylneuraminic acid synthetase.

Herrn KollegenK. Schlögl mit den besten Wünschen zum 60. Geburtstag.     

Strukturelle Abwandlungen an Kohlenhydraten, 7. Mitt.

The synthesis of the title compound from 1,2:5,6-Di-O-isopropyliden-α-D-glucofuranose (1) via 1,2:5,6-Di-O-isopropyliden-α-D-gulofuranose (4) is reported. The key-step is the introduction of the azido function into4 which is achieved by using Triphenylphosphane/Diethylazodicarboxylate/HN₃.     

Strukturelle Änderungen im glasigen Polyäthylenterephthalat

Ohne Zusammenfassung     

Strukturelle und magnetische Untersuchungen an Hexachlorowolframaten(V)

Structural and Magnetic Investigations of Hexachlorotungstates(V) CsWCl₆ crystallizes in the monoclinic space group C2/c with the lattice dimensions a = 12.097(8), b = 6.327(5), c = 15.30(1) Å, β = 128.4(1)° and 4 formula units. The compounds AWCl₆ (A = Rb, K, NH₄) are isotypic with CsWCl₆ as shown by powder patterns. Single-crystal photographs of [N(C₂H₅)₄]WCl₆ show monoclinic symmetry, space group P2₁/n with a = 11.737(8), b = 10.239(7), c = 7.191(5), β = 101.46(8)° and Z = 2. Both structures are composed of scarcely deformed WCl₆ octahedra. The trigonal compression of the octahedra results in a slightly negative deformation parameter according to the Figgis-model of the magnetic behaviour of d¹-systems. Above 80 K the μ² vs. T-curve is linear. This leads to a spin-orbit coupling constant of 1250 ± 200 cm^?1 and a covalence parameter of 0.6–0.8. Comparing the spectra of WCl₆, CsWCl₆ and Cs₂WCl₆ the beginning of the charge-transfer region was determined. The crystal field strength for CsWCl₆ was found as Δ = 16 000 cm^?1.     

Analytische Aspekte der Photo-Polarographie

Zusammenfassung Ein analytisches Interesse besitzen Photo-Depolarisatoren und photoreaktionsbedingte Diffusionsströme.Die zur Zeit häufigsten Photo-Depolarisatoren sind Radikale, die unmittelbar nach Photogenerierung oder nach ihrer Anregung Elektronen mit der Elektrode austauschen. Überwiegt bei ihnen die photochemische Weiterreaktion, so kann deren Quantenausbeute aus dem zugehörigen photoreaktionsbedingten Oxydationsstrom insbesondere bei Ketylen bestimmt werden.

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Summary Photo-depolarizers and diffusion currents caused by photoreaction are of some interest from the analytical point of view. Mostly investigated are free radicals, which are able to exchange electrons with the electrode surface after photogeneration or immediately after excitation. In the case of photochemical forward-reaction of the radicals the quantum requirement may be measured by means of the photoreaction-caused oxidation current, especially with ketyls.

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17. Mitt, über Photo-Polarographie. — 16. Mitt. vgl. Berg, H., u. F. A. Gollmick: Collection Czech. Chem. Commun, (im Druck) (1965).