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11.
Ohne Zusammenfassung7. Mitt.:Hermann Schmid undG. Bauer, Mh. Chem.96, 1508 (1965); dort ältere Mitt. dieser Reihe zitiert. 相似文献
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The gas-phase rearrangement of (1Z, 2′E)-, (1Z, 2′Z)-, (1E, 2′E)-, and (1E, 2′Z)- propenyl but-2′-enyl ether (Z, E)-, (Z, Z)-, (E, E)-, and (E, Z)-1) into erythro- and threo-2, 3-dimethyl-pent-4-en-al (erythro- and threo-2) was investigated over a temperature range from 142,5° to 190,0° at 20–35 Torr (for kinetic data and activation parameters see table 2). All four stereoisomeric ethers 1 rearrange preferentially via a chair-like transition state C into the aldehydes 2 (ΔΔG≠ (160°) = 2,5–2,7 kcal/mol for B – C (B = boat-like transition state). The relative rates (krel) for (Z, Z)-1, (Z, E)-1, (E,Z)-1, and (E,E)-1 at 160° are 1,0, 2,9, 4,3 and 9,0 respectively (see table 5). Taking into account the relative enthalpies of the ethers 1 and the steric interaction in the C transition state of the ethers 1 (see table 6), krel values can be estimated. They are in good agreement with those observed (see table 5). 相似文献
14.
Zusammenfassung Die Herstellung von festen Komplexen des Uran(IV) mit Di-n-butylphosphorsäure in Kontakt mit Perchlor-, Schwefel-und Salpetersäure wird beschrieben. Es ergab sich für die beiden ersten Fälle eine Zusammensetzung U(DBP)4 und für den letzten U(NO3)(DBP)3, wobeiDBP für das Anion der Di-n-butylphosphorsäure steht. Auf Grund der Infrarotspektren im Bereich von 4000 bis 700 cm–1 wurde versucht, Anhaltspunkte über die Bindungsverhältnisse in den Komplexen zu erhalten. Die Absorptionsbanden des U(NO3)(DBP)3-Komplexes bei 1520 und 1275 cm–1 weisen darauf hin, daß das Nitrat im wesentlichen kovalent an das Uran(IV) gebunden ist.
Mit 1 Abbildung
Herrn Prof. Dr.O. Kratky zum 70. Geburtstag gewidmet. 相似文献
The preparation and characterization of solid complexes of uranium(IV) with di-n-butyl phosphoric acid in contact with perchloric, sulfuric and nitric acid solutions
The preparation of solid complexes of uranium(IV) with di-n-butyl phosphoric acid in contact with aqueous perchloric, sulfuric and nitric acid solutions is described. The formula was found to be U(DBP)4 for the complexes prepared in contact with the two first mentioned acids, and U(NO3)(DBP)3 for the complex prepared in contact with HNO3 (DBP stands for the anion of the di-n-butyl phosphoric acid). Absorption spectra were registered in the infrared region from 4000–700 cm–1. Due to the absorption bands at 1520 and 1275 cm–1 it seems, that the nitrato group is bound mainly covalent in the U(NO3)(DBP) complex.
Mit 1 Abbildung
Herrn Prof. Dr.O. Kratky zum 70. Geburtstag gewidmet. 相似文献
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Sabine Schmid 《Journal of solid state chemistry》2003,174(1):221-228
The novel alkaline earth silicate borate cyanides Ba7[SiO4][BO3]3CN and Sr7[SiO4][BO3]3CN have been obtained by the reaction of the respective alkaline earth metals M=Sr, Ba, the carbonates MIICO3, BN, and SiO2 using a radiofrequency furnace at a maximum reaction temperature of 1350°C and 1450°C, respectively. The crystal structures of the isotypic compounds MII7[SiO4][BO3]3CN have been determined by single-crystal X-ray crystallography (P63mc (no. 186), Z=2, a=1129.9(1) pm, c=733.4(2) pm, R1=0.0336, wR2=0.0743 for MII=Ba and a=1081.3(1) pm, c=695.2(1) pm, R1=0.0457, wR2=0.0838 for MII=Sr). Both ionic compounds represent a new structure type, and they are the first examples of silicate borate cyanides. The cyanide ions are disordered and they are surrounded by Ba2+/Sr2+ octahedra, respectively. These octahedra share common faces building chains along [001]. The [BO3]3− ions are arranged around these chains. The [SiO4]4− units are surrounded by Ba2+/Sr2+ tetrahedra, respectively. The title compounds additionally have been investigated by 11B, 13C, 29Si, and 1H MAS-NMR as well as IR and Raman spectroscopy confirming the presence of [SiO4]4−, [BO3]3−, and CN− ions. 相似文献
18.
Recent advances in chiral separation principles in capillary electrophoresis and capillary electrochromatography 总被引:3,自引:0,他引:3
This review summarizes recent developments in chiral separation in capillary zone electrophoresis (CZE), electrokinetic chromatography (EKC), and capillary electrochromatography (CEC) covering literature published since the year 2000. New chiral selectors and innovative approaches for CE and CEC are introduced. Recent progress in column technology for CEC is highlighted and the development of new chiral stationary phases is discussed. This review is not dedicated to list applications but will focus on new developments. 相似文献
19.
Abstract— The photosynthetic activity of white light-grown Acetabularia mediterranea Lamouroux (= A. acetabulum (L.) Silva) decreases under continuous red light to less than 20% within 3 weeks. Subsequent blue light reactivates photosynthesis within a relatively short period of 3 days. In a former publication (Wennicke and Schmid, Plant Physiol. 84 ,1252–1256, 1987) we have shown that the regulated rate limiting step, which is an immediate light driven reaction, is part of photosystem II (PS II). The following biophysical properties of PS II were analyzed in thylakoids isolated from algae grown 3 weeks under either blue or red light with or without subsequent 3 days of blue light illumination: (a) fluorescence induction in the short time domain dominated by QA reduction, (b) the slow fluorescence decline reflecting pheophytin photoaccumulation, (c) absorption changes at 320 and 830 nm under repetitive flash excitation as indicator for the turnover of QA and P680 , respectively, (d) oscillation pattern of the oxygen yield by a flash train in dark adapted samples and (e) the binding capacity for atrazine. None of these PS II functions were severely affected, but a minor impairment of20–30% was observed in the thylakoids from algae grown for 3 weeks in red irradiation. The changes do not fully account for the drastic reduction of the electron transport through PS II which was 80% after red light treatment. Therefore, the regulated rate-limiting step appears to not be mainly located in the PS II core complex itself. It seems likely that the regulation process predominantly comprises the antenna system. 相似文献
20.
Eva BeckerChristian Slugovc Eva RübaChristina Standfest-Hauser Kurt MereiterRoland Schmid Karl Kirchner 《Journal of organometallic chemistry》2002,649(1):55-63
The synthesis and some reactions of the Ru(II) and Ru(IV) half-sandwich complexes [RuCp(EPh3)(CH3CN)2]+ (E=P, As, Sb, Bi) and [RuCp(EPh3)(η3-C3H5)Br]+ have been investigated. The chemistry of this class of compounds is characterized by a competitive coordination of EPh3 either via a RuE or a η6-arene bond, where the latter is favored when the former is weaker, that is in going down the series. Thus in the case of Bi, the starting material [RuCp(CH3CN)3]+ does not react with BiPh3 to give [RuCp(BiPh3)(CH3CN)2]+ but instead gives only the η6-arene species [RuCp(η6-PhBiPh2)]+ and [(RuCp)2(μ-η6,η6-Ph2BiPh)]2+. Similarly, the EPh3 ligand can be replaced by an aromatic solvent or an arene substrate. Thus, the catalytic performance of [RuCp(EPh3)(CH3CN)2]+ for the isomerization of allyl-phenyl ethers to the corresponding 1-propenyl ethers is best with E=P, while the conversion drops significantly using the As and Sb derivatives. By the same token, only [RuCp(PPh3)(CH3CN)2]+ is stable in a non-aromatic solvent, whereas both [RuCp(AsPh3)(CH3CN)2]+ and [RuCp(SbPh3)(CH3CN)2]+ rearrange upon warming to [RuCp(η6-PhEPh2)]+ and related compounds. In addition, the potential of [RuCp(EPh3)(CH3CN)2]+ as precatalysts for the transfer hydrogenation of acetophenone and cyclohexanone has been investigated. Again aromatic substrates are clearly less suited than non-aromatic ones due to facile η6-arene coordination leading to catalyst's deactivation. 相似文献