Peritektische Zersetzung von YBa2Cu3O7−x

During the heating of YBCO a peritectic reaction takes place at 1020C, which can be described by: 2YBa₂Cu₃O_7–xY₂BaCuO₅+L+(1-2x)/2O₂ (1) whereL = 3BaCuO₂ +2CuO is a fluid with limited amount of yttrium.It has been reported, that many parameters can influence the reaction. From one side not only the starting size of grains but also the heating rate have an influence on the resulting Y₂BaCuO₅-phase. From the other side, there is a change of the peritectical temperature caused by changing of the partial pressure of O₂ and the presence of parasitic phase.From general kinetic consideration one can draw the conclusion, that different mechanisms (nucleation, phase-boundary reaction and diffusion) can control the reaction.Using DTA/TG measurements, the peritectic reaction has been examined. Classical kinetic methods (Kissinger and Friedman) has been used. The Friedman method has given the dependence of the activation energy from reaction degree. This suggests many steps reactions. The dependence of the DTA-peaks from the heat rate suggest a parallel steps of reaction. This assumption can be motivated by evaluation of free O₂, one solid and liquid phase formation. Amount of this phases depends on the heating rate. Additionally X-ray and microscopic methods has been used. In this way was shown, that the perovskit structure is stable up to peritectical temperature and than is dramatically destroyed. From microscopic observations has been got information about shape and size of solid phase and it's creation as a function of temperature, time and starting grain size.

Die Arbeit wurde BMBF gefördert und durch Land NRW unterschtützt.     

铟(Ⅲ)-7-(1-苯偶氮)-8-羟基喹啉-5-磺酸钠的配位吸附波及其应用

在ｐＨ４．５的 ０．０１５ ｍｏｌ／Ｌ ＨＡｃ－ＮａＡｃ介质中，Ｉｎ铟（Ⅲ）－７－（１－苯偶氮）－８－羟基喹啉－５－磺酸钠（ＢＱ）在滴汞电极上于－０．６６５－０．７０ Ｖ（ｖｓ．ＳＣＥ）电位处得到络合物的吸附还原波，其一阶导数峰电流Ｉ＇ｐ与Ｉｎ（Ⅲ）浓度在４．０× １０~（－８）～３．５ × １０~（－６）ｍｏｌ／Ｌ范围内呈良好的线性关系，检测限为１．６ × １０~（－８）ｍｏｌ／Ｌ Ｉｎ（Ⅲ）．应用该法测定了铅粉和氢氧化铝样品中的微量铟，结果令人满意。对电极反应机理进行了探讨。     

Crystal Structure of (6S,9S,13R,14S)-7,8-Didehydro-3,7-dimethoxy-17-methylmorphinan-4,6-diol

1 INTRODUCTION (9S,13R,14S)-7,8-Didehydro-3,7-dimethoxy-4-hydroxy-17-methylmorphinan-6-one I is an impor- tant natural product that was used to ease pain, decrease blood pressure and diminish inflammation. In order to study the stereochemistry of the reduction of I with potassium boronhydride, the crystal structure of the title compound II was determined by X-ray diffraction method. 2 EXPERIMENTAL 2. 1 Instrument The melting point was measured on a Yanagimoto MP-500 apparatus…     

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.     

Halbsandwichkomplex des Chroms mit dem Trifluormethylisocyanid-Liganden

Halfsandwich Complexes of Chromium with the Trifluoromethyl Isocyanide Ligand The synthesis and properties of the halfsandwich complexes [η⁶-1,3,5-C₆H₃(CH₃)₃]Cr(CO)₂(CNCF₃), [η⁶-1,3,5-C₆H₃(CH₃)₃]Cr(CO)(CNCH₃)(CNCF₃) und [η⁶-1,3,5-C₆H₃(CH₃)₃]Cr(CNCF₃)₃ is reported. The vibrational spectroscopic data proof the strong π accepting character of the trifluoromethyl isocyanide ligand.     

Interaction of aminoazoles with Meldrum’s acid and dialkyl ketones or cyclohexanone

Interaction of 3-amino-5-methylpyrazole, 3-amino-5-methylthio-, and 3,5-diamino-1,2,4-triazole with Meldrum’s acid, acetone, ethyl methyl ketone, and cyclohexanone leads to alkyl-substituted pyrazolo[3,4-b]pyridin-6-ones and 1,2,4-triazolo[1,5-a]pyrimidin-7-ones respectively. The structure of 5,5-dimethyl-2-methylthio-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]pyrimidin-7-one was demonstrated by an X-ray structural investigation. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 595–601, April, 2007.     

Composite Pd/Pr4O7/C catalysts: Synthesis, dispersity and properties

The catalysts prepared sequentiallyvia the interaction of C₃H₅PdC₅H₅ with the surface of evacuated Pr₄O₇/C and reduction with H₂ at 573 K, contain 20–30 Pd particles and Pr₄O₇ particles<20 . The catalysts obtained have two-order of magnitude higher specific activity in the CH₃OH synthesis than Pd/C.     

Bioanalytical methods applied to endocrine disrupting polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans. A review

The usual methods for determining polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and polychlorinated biphenyls (PCB) are generally expensive and time consuming. This fact has favored the development of faster and cheaper techniques, based on immunoassays and bioassays. This paper reviews these bioanalytical methods and their analytical importance at the present moment.     

Alkylation of cyclododecanone with α,ω-dibromoalkanes under conditions of phase-transfer catalysis

Alkylation of cyclododecanone with ,-dibromoalkanes Br(CH) _n Br (n=3, 4, 5) under conditions of phase-transfer catalysis in the presence of KOH results in the formation of either bicyclic ketones forn=3 and 5 or a mixture of bicyclic and spirocyclic ketones forn=4.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1436–1438, August, 1994.     

Anomalous hydroalumination of methyl nopol ether with a LiAlH4-3AlBr3 system

Hydroalumination of methyl nopol ether with a LiAlH₄-3AlBr₃ system is accompanied by a skeleton rearrangement and gives 6-dibromoalumo-7-methoxymethyl-2-menthene. Further hydroalumination affords a mixture of 2,6- and 2,5-bis(dibromoalumo)-7-(methoxymethyl)menthanes in 8020 ratio. Hydrolysis and oxidation of these organoaluminum compounds were carried out.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 506–510, March, 1994.