Preparation and characterization of bis(cyclopentadienyl)zirconium (IV) oximate complexes

Summary Oximate complexes of bis(cyclopentadienyl)zirconium(IV) chloride (Cp₂ZrCl₂ ) having the general formulae Cp₂Zr(Ox), Cp₂Zr(OxH)Cl and Cp₂Zr(OxH)₂ [where OxH₂ = RC₆H₄C(OH)R: NOH, R = H, Me, R= H, Me, Et, n-Pr; PhC: N(OH)CH(OH)Ph and RC : N(OH)N(OH): CR, R = H, Me and Ph] have been synthesized by reacting bis(cyclopentadienyl)zirconium(IV) chloride with the appropriate oxime in tetrahydrofuran in the presence of triethylamine at room temperature. The complexes have been characterized by their elemental analysis, i.r. and electronic spectra, molecular weight determination, electrical conductance and magnetic measurements.Reprints of this paper are not available.     

Katalytischer Wasserstoffaustausch des Äthans am Nickelkatalysator

Zusammenfassung Der Wasserstoffaustausch zwischen Äthan und Deuterium bzw. Tritium wird an Nickelpulver als Katalysator untersucht. Die auf Wasserstoff bezogene Reaktionsordnung nimmt im Temperaturgebeit 147–323°C zu, während die in bezug auf Äthan sich konträr verändert. Auch die Aktivierungsenergie nimmt ein wenig ab. Die Ergebnisse der Untersuchungen mittels Deuterium zeigen, daß die Hauptprodukte des Austausches Äthan-d₂ und Äthan-d₆ sind. Das Verhältnis der Anfangsgeschwindigkeiten der Bildung beider Produkte hängt von der Katalysatoraktivität und der Temperatur ab. Auf Grund des Vergleichs dieser Ergebnisse mit denen des Methanaustausches kann der große Unterschied im Verhalten beider Stoffe durch die Verschiedenheit der Adsorptionsmechanismen erklärt werden.

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Catalytic hydrogen exchange reaction of ethane over aNi catalyst

The hydrogen exchange between ethane and deuterium as well as tritium has been investigated over nickel powder catalyst. In the temperature range from 147 to 323°C the order of reaction with respect to hydrogen increases whereas for ethane the reverse is observed. The activation energy also decreases slightly. The study with deuterium showed that the main products of exchange were ethane-d₂ and ethane-d₆. The ratio of the initial rater of formation of these products depended on the catalyst activity and the temperature. By comparing these results with those of methane exchange the large difference in behaviour between methane and ethane can be ascribed to the difference in adsorption mechanism.

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Mit 4 Abbildungen

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Herrn Prof. Dr.E. Broda zum 60. Geburtstag gewidmet.     

Fuzzy automata based on lattice-ordered monoid with algebraic and topological aspects

The purpose of this work is to study some algebraic and topological concepts of fuzzy automata with the membership values in lattice-ordered monoids. Unlike the usual fuzzy automata, we show that such concepts are affected by the associated monoid structure.     

Fission fragment angular distributions in 16O+181Ta

Time of flight and energy of fission fragments were measured using pulsed beam. Fission fragment mass and energy integrated angular distributions were extracted. Fission fragment anisotropy was explained in the framework of saddle point model.     

Measurement of fission anisotropy for 16O+181Ta

Anisotropies in fission fragment angular distributions measured for the system ¹⁶O + ¹⁸¹Ta over a range of bombarding energies from 83 MeV to 120 MeV have been analysed. It is shown that statistical transition state model (TSM) with pre-scission neutron correction described adequately the measured anisotropy data. Strong friction parameter is found to be necessary to estimate the pre-saddle to pre-scission neutron ratio.     

On Zeros of One Class of Functions Analytic in a Half-Plane

We describe sequences of zeros of functions f 0 analytic in the half-plane and satisfying the condition where : [0; +) (0; +) is an increasing function such that the function ln (r) is convex with respect to ln r on [1; +).     

An Integrated LC-ESI-MSn and High Resolution LC-ESI-QTOF Approach for the Identification of Phloroglucinols from Nepalese Hypericum japonicum

Phloroglucinols are characteristic constituents of Hypericum japonicum that are claimed to exert several bioactivities, such as anti-inflammatory, anti-depressant and anti-viral ones. Phloroglucinols are unstable compounds and their synthesis is challenging; thus, isolation from natural sources is still one of the main strategies for obtaining these constituents in purified form. Assessing the presence of phloroglucinols in plant materials can be of interest for compound isolation, and LC-MS approaches afford sensitivity and specificity in this regard. In this work, we combined data from quadrupole-time of flight (QTOF) and ion trap (IT) mass spectrometers in order to assess the presence of the phloroglucinols characteristic of H. japonicum and to elucidate their MS fragmentation pathways. The identified compounds present similar structures bearing the 1,3,5-trihydroxybenzene core with different substitutions, which, in constituents at higher MW, is linked to 3′,3′-dimethyl-6′-oxo-phlorisobutyrophenone by a methylene bridge. Differences in MS² spectra of the considered phloroglucinols are useful for compound identification and differentiation, and to perform dereplication studies. Overall, the proposed approach could be useful for the analysis of phloroglucinols in H. japonicum and other plant species.     

Efficient One-Pot Synthesis of 4-Aroyl-2-pyrones: Nucleophilic Addition of Active Methylene Groups to 1,2-Diaroylacetylenes

An efficient synthesis of 3,6-disubstituted-4-aroyl-2-pyrones in a single-step reaction through Michael addition of 1,2-diaroylacetylenes with active methylene compounds in the presence of NaH in dimethylsulfoxide at room temperature is reported. The structures have been confirmed by spectral data analyses.