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11.
12.
Jerzy Lange Elzbieta Pytlewska Jan Plenkiewicz Tomasz Kulinski Janina Karolak-Wojciechowska Slawomir Rump 《Journal of heterocyclic chemistry》1997,34(2):389-396
Ethoxycarbonylalkylidene derivatives 2 and 6 of the title hydrazones were obtained in the reaction with ethyl pyruvate or ethyl aroylformate and ethyl acetoacetate, respectively, in methanol. Both compounds were mixtures of geometric isomers with high predominance of one of them. Nmr spectroscopy revealed an unexpected magnetic non-equivalence of the CH2 protons in the ester ethyl group of the major isomer of 6 . On heating (?200°) in an inert medium or on refluxing in ethanolic sodium ethoxide 2 cyclized to the corresponding pyridazino[6,1-c]-triazines 4 , whereas 6 formed pyrazolylpyridazines 7 . The structure of the latter was unambigously established by X-ray analysis. Alkylation of 4a with benzyl bromide in the presence of tetrabutylammonium bromide occurred selectively on the pyridazine N atom. 相似文献
13.
14.
T. A. Przylibski B. Kozłowska J. Dorda B. Kiełczawa 《Journal of Radioanalytical and Nuclear Chemistry》2002,253(1):11-19
This work characterizes the occurrence of radionuclides 222Rn and 226Ra in the mineralized groundwaters of Gorzanów. The village is situated in the Sudeten Mountains, which are known in Poland for having increased concentrations of the aforesaid radionuclides in their groundwaters. However, in Gorzanów, the measured concentrations of 226Ra were low both in the reservoir rocks and mineralized waters. Consequently, the 222Rn concentration in the groundwaters also turned out to be low. The 226Ra content of these waters should mainly be associated with the dissolution of this nuclide, together with other main ions, at large depths, at slightly enhanced temperature. Radon-222, on the other hand, penetrates into the water during its outflow to the surface, in the zones of intensive friable deformations near fault zones. Thus, in the groundwaters of Gorzanów, the concentrations of these nuclides, subsequent in the uranium series, do not have a common genesis and they are not correlated with each other. 相似文献
15.
Mono(6-deoxy-dimethylpyridinium)-β-cyclodextrins have been synthesized in reaction of mono (p-toluenesulfonyl) derivative
of β cyclodextrin with the appropriate lutidine under microwave irradiation and conventional conditions. The results indicate
that the mechanism consists of inclusion complex formation. 相似文献
16.
Mojumdar S. C. Kozánková J. Chocholoušek J. Majling J. Fábryová D. 《Journal of Thermal Analysis and Calorimetry》2004,78(1):73-82
Fluoroapatite containing glass-ceramics were prepared from Li2O-CaO-CaF2-P2O5-SiO2 system. The glass was melted at 1480°C for 1 h. The object of observation was the preparing crystal phase of fluoroapatite
in amorphous glass matrix. The morphology of lithium disilicate glass-ceramics was studied by SEM. The crystal growth and
thermal properties of fluoroapatite were studied by X-ray diffraction and DTA. The more the content of P2O5, the more the presence of fluoroapatite particles. SEM investigation clearly indicated the phase separation and formation
of a primary crystalline phase of fluoroapatite in the studied glass-ceramics. DTA curves of the fluoroapatite samples exhibit
exothermic effects in the temperature range 337-694°C depending on the composition of the materials. The position of exothermic peak for lithium disilicate on DTA curves moves with increasing specific surfacetowards lower temperatures which points on its preferential surface crystallization. As far as physical qualities are concerned,
mainly color and gloss, the best qualities of all observed materials belong to glass-ceramics with 10% P2O5.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Robert Pietrzak Mieczysław Kozłowski Helena Wachowska Jan Yperman 《Central European Journal of Chemistry》2004,2(2):278-289
Soluble products obtained from the oxidation of four types of coal, each characterised by different degree of coalification
and different degree of sulphur content, are studied. The coals are oxidised with peracetic acid (PAA) and nitric acid. Analyses
are performed by Atmospheric Pressure-Temperature Programmed Reduction (AP-TPR) and Fourier Transform Infrared Spectroscopy
(FTIR). The soluble products contain much more sulphur than the insoluble products of oxidation. The products obtained from
the reaction with HNO3 contain higher amounts of inorganic sulphur compounds, while those obtained from the reaction with PAA are characterised
by an increased content of organic sulphur species. 相似文献
18.
Tomasz Klis Sergiusz Lulinski Janusz Serwatowski 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(3):o145-o146
The molecule of the title compound, 2,3‐F2‐4‐(CHO)C6H2B(OH)2 or C7H5BF2O3, contains a formyl group coplanar with the benzene ring. The boronic acid group is twisted with respect to the benzene ring plane. The molecules are organized into infinite chains via intermolecular O—H⋯O hydrogen bonds. These chains are additionally connected via strong O—H⋯O hydrogen bonds, producing a folded layer structure perpendicular to the a axis. These layers are paired due to B⋯F interactions. 相似文献
19.
Designs, Codes and Cryptography - The problem of classifying linear systems of conics in projective planes dates back at least to Jordan, who classified pencils (one-dimensional systems) of conics... 相似文献
20.
JPC – Journal of Planar Chromatography – Modern TLC - A ten-component mixture of pesticides was applied to the edge of the layer in ‘frontal + elution’ mode for preliminary... 相似文献