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11.
(Eta6-arene)tricarbonylchromium 2 was synthesised by [3+2+1] benzannulation of the Fischer carbene complex 1 and converted to the thermodynamically more favorable regioisomer 3 by haptotropic metal migration. Photo-induced ligand-exchange reactions in both regioisomers with triphenylphosphine, triphenylphosphite, trimethylphosphine, and trimethylphosphite afforded dicarbonyl(phosphine or phosphite)arene complexes 4-11. The regioisomers were separated by high-performance liquid chromatography (HPLC), and kinetic analyses of the thermo-induced haptotropic metal shift were performed with regioisomers 4, 6, 8, and 10. The kinetic parameters were compared with those obtained for the parent tricarbonyl complex 2 and were discussed in terms of the steric and electronic properties of the phosphorus ligands by applying a quantitative analysis of ligand effects (QALE). The molecular structures of regioisomeric PPh3 and P(OPh)3 complexes 4/5 and 6/7 as well as of P(OMe)3 complex 10 have been established by single-crystal X-ray analysis. 相似文献
12.
R. Jahr K. D. Müller W. Oswald U. Schmidt-Rohr 《Zeitschrift für Physik A Hadrons and Nuclei》1961,161(5):509-524
The spectra of deuterons scattered from C, Mg, Ti, Fe, Ni, Cu and Zn have been measured in steps of 5° betweenΘ lab=20° and 165°. The excitation of the lowest levels is in most nuclei strongly preferred and only very few low energy deuterons were observed. The angular distributions of the elastic and inelastic scattering of deuterons show pronounced diffraction maxima which are partly correlated. The correlation is compared with the Blair-model. 相似文献
13.
H. O. Günther K. Santarius und D. Jahr 《Fresenius' Journal of Analytical Chemistry》1982,311(4):401-402
Ohne Zusammenfassung
Detection of phenolic, naturally occurring oestrogens in body fluids and food by an enzyme-immuno-assay (ELISA)相似文献
14.
Peter Binnemann und Dieter Jahr 《Fresenius' Journal of Analytical Chemistry》1979,297(5):341-356
Zusammenfassung Es wird ein Überblick über die Vielzahl der Anwendungsmöglichkeiten massenspektrometrischer Analysenverfahren im Bereich der Überwachung von Lebensmitteln und Bedarfsgegenständen gegeben. Nach einer kurzen Darstellung der erforderlichen Geräteausstattung wird auf die Untersuchung der wichtigen Lebensmittelbestandteile Fette, Kohlenhydrate, Aminosäuren und Aromastoffe eingegangen. Anschließend werden die Zusatzstoffe behandelt.In einem weiteren Teil werden massenspektrometrische Bestimmungen der wichtigsten Verunreinigungen und Schadstoffe in Lebensmitteln sowie die Untersuchung von Bedarfsgegenständen dargestellt werden.
Application of mass spectrometry in the control of food and consumer articles. I
Summary A review is given on the numerous possibilities of applying mass spectrometry in the control of food and consumer articles. After a short presentation of the necessary equipment, the investigation of lipids, carbohydrates, amino acids and flavours is discussed. Subsequently, food additives are dealt with.In a further part the mass spectral analysis of the most important contaminants and hazardous pollutants in food will be reviewed and the investigation of consumer articles will be outlined.相似文献
15.
Angular distributions of deuterons and tritons from the reactions52,53Cr(d,d),52,53Cr(d,d′),53,54Cr(d, t)52,53Cr have been measured at Ed=11.8 to 11.9 MeV. The elastic scattering data have been analyzed in terms of the optical model. The (d, d′) and (d, t) data have been compared with DWBA calculations. Deformation parameters and spectroscopic factors have been extracted. The results are qualitatively discussed in terms of different nuclear models. 相似文献
16.
Enantioselective Organocatalytic Cascade Approach to Different Classes of Benzofused Acetals 下载免费PDF全文
Bruno Matos Paz Dr. Lydia Klier Line Næsborg Vibeke Henriette Lauridsen Prof. Dr. Frank Jensen Prof. Dr. Karl Anker Jørgensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):16810-16818
A novel enantioselective organocatalytic strategy is presented for the synthesis of tetrahydrofurobenzofuran and methanobenzodioxepine natural product core structures. The strategy is based on a pair of divergent reaction pathways in which hydroxyarenes react with γ‐keto‐α,β‐unsaturated aldehydes, catalyzed by a chiral secondary amine. One reaction pathway, which leads to chiral 5,5‐fused acetals with two stereocenters—the tetrahydrofurobenzofuran scaffolds—proceeds in moderate yields and up to 96 % ee. The other reaction pathway provides 5,6‐bridged methanobenzodioxepine scaffolds with three stereocenters in moderate to good yields and up to 95 % ee. The reaction is remarkable as it can proceed with catalyst loadings as low as 0.25 mol %, providing one of the highest known turnover numbers in iminium ion catalysis. Furthermore, the hemiacetal tetrahydrofurobenzofuran can undergo functionalizations including reduction, oxidation, and allylation. Finally, the effects involved in the substrate control for the divergent pathways, based on both experimental and computational studies, have been investigated. A model involving steric, electronic and stereoelectronic interactions is discussed to rationalize the observed selectivities. 相似文献
17.
Asymmetric Brønsted Base Catalyzed and Directed [3+2] Cycloaddition of 2‐Acyl Cycloheptatrienes with Azomethine Ylides 下载免费PDF全文
Vibeke H. Lauridsen Lise Ibsen Jakob Blom Prof. Dr. Karl Anker Jørgensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3259-3263
Conjugated cyclic trienes have the potential for different types of cycloaddition reactions. In the present work, we will, in a novel asymmetric cycloaddition reaction, demonstrate that the organocatalytic reaction of 2‐acyl cycloheptatrienes with azomethine ylides proceeds as a [3+2] cycloaddition, which is in contrast to the Lewis acid‐catalyzed reaction, in which a [3+6] cycloaddition takes place. In the presence of a chiral organosuperbase, 2‐acyl cycloheptatrienes react in a highly enantioselective manner in the [3+2] cycloaddition with azomethine ylides, providing the 1,3‐dipolar cycloaddition product in high yields and up to 99 % ee. It is also shown that the diene formed by the reaction can undergo stereoselective dihydroxylation, bromination, and cycloaddition reactions. Finally, based on experimental observations, some mechanistic considerations are discussed. 相似文献
18.
J. O. Burton R. H. Rasch J. L. Parsons J. H. Ross H. Braidy H. Gault B. C. Mukerji J. D. Piper C. H. Fellows T. Hamburger W. Brecht W. Staedel J. Bekk H. Wenzl P. Wolski E. C. Hendrickson V. Gruenman G. H. Mc Gregor G. K. Bergman C. B. Björkman A. Tingle B. v. Possanner R. A. Krauss W. Henneberg J. Lifschütz G. Lebbin A. Kiesel N. Semiganowsky W. Fuchs R. Sieber R. Willstätter L. Zechmeister Th. von Fellenberg E. Heuser W. Niethammer S. Schmidt-Nielsen Teicher H. L. Jaochim M. G. Kotibhasker J. Croland E. Asker Klemm Korn Mäule G. Jander K. F. Jahr Hennig 《Analytical and bioanalytical chemistry》1934,97(3-4):133-144
19.
20.
Striking presence of Egyptian blue identified in a painting by Giovanni Battista Benvenuto from 1524
Bredal-Jørgensen J Sanyova J Rask V Sargent ML Therkildsen RH 《Analytical and bioanalytical chemistry》2011,401(4):1433-1439
Egyptian blue has been identified in a painting from 1524 by the Italian artist Ortolano Ferrarese (Giovanni Battista Benvenuto).
Egyptian blue is the oldest known synthetic pigment, invented by the Egyptians in the fourth dynasty (2613–2494 bc) of the Old Kingdom and extensively used throughout Antiquity. From about 1000 a.d., it disappeared from the historical record and was only reinvented in the late nineteenth and early twentieth century. The
discovery of Egyptian blue in Ortolano Ferrarese’s painting from 1524 shows that Egyptian blue was in fact available in the
period from which it is normally considered not to exist. The identification of Egyptian blue is based on optical microscopy
supported by energy-dispersive spectroscopy and visual light photon-induced spectroscopy, and finally confirmed by Raman microspectroscopy. 相似文献