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71.
Dunne KS Bisaro F Odell B Paris JM Gouverneur V 《The Journal of organic chemistry》2005,70(26):10803-10809
[reaction: see text] The preparation of phosphorus-containing trienes featuring two diastereotopic vinyl moieties followed by a diastereoselective ring-closing metathesis is described. This methodology allowed for the synthesis of novel highly functionalized P-stereogenic heterocycles featuring both an exo- and an endocyclic double bond. An investigation into the factors influencing the diastereochemical outcome of the ring-closing metathesis is also presented, revealing that the geometry of the double bonds conjugated to phosphorus is important and that 1,3-stereoinduction is superior to 1,4-stereoinduction for these reactions. 相似文献
72.
Triphenylphosphane Nickel(0) Complexes with Isocyanide Ligands — [(RNC)nNi(PPh3)4–n] (n = 1–3) Synthesis and properties of the isocyanide triphenylphosphane nickel(0) complexes [(RNC)Ni(PPh3)3], [(RNC)2Ni(PPh3)2] and [(RNC)3Ni(PPh3)] (R = tBu, Cy, PhCH2, p-TosCH2) are described. I.r. and 31P n.m.r. spectra were recorded and the X-ray crystal structure of [(PhCH2NC)2Ni(PPh3)2] was determined. 相似文献
73.
The mass spectra of several dibenzo (d.f)-1,3,2,-dioxaphosphorepines of the type where X=0, S, Se and R=2,2′-biphenylylene, have been studied. Dibenzochalcogen ions [RX]+˙ stemming directly from [M]+˙ were observed with high intensities, indicating specific migration of X from phosphorus to carbon with simultaneous destruction of the dioxaphosphorepine ring. Simple cleavage of P? Y as usually observed in similar organophosphorus compounds is not a common process here. 相似文献
74.
Vendeuvre C Bertoncini F Thiébaut D Martin M Hennion MC 《Journal of separation science》2005,28(11):1129-1136
Modeling the retention in comprehensive two-dimensional gas chromatography (GC x GC) was achieved using retention indices obtained in conventional GC. Predicted results were compared with experimental data obtained in the two-dimensional separation of a synthetic hydrocarbon mixture. This proved to be helpful in optimizing the operating conditions of GC x GC separation of a complex petroleum sample and in identifying chemical families. 相似文献
75.
Wilhelm Prodinger 《Mikrochimica acta》1960,48(5-6):766-770
Zusammenfassung Na-cyklohexyldithiocarbaminat reagiert im pH-Bereich 6,6 bis 7,2 mit Uranylsalzen unter Bildung eines in Wasser mit gelber Farbe lösliehen Komplexes, der bei pH 6,6 ein Absorptionsmaximum bei 392 bis 394 nm besitzt. Die wäßrige Lösung wird durch Zusatz von Alkalilauge bis zum pH 8 bis 9 momentan entfärbt.Es wird ein Kaliumdoppelsalz KUO2(S2HCNC6H11)3 · 3 H2O beschrieben; ferner wird über die Umwandlung des Calciumdoppelsalzes beim Kochen mit NaOH berichtet.
Gewidmet zur 100. Wiederkehr des Geburtstages vonFriedrich Emich. 相似文献
Summary Sodium cyolohexyldithiooarbamate reacts, in the pH range 6.6 to 7.2, with uranium salts to yield a complex which gives a yellow aqueous solution. The absorption maximum is at 392–394 nm at pH 6.6. The aqueous solution loses its color immediately when caustic alkali is added to raise the pH to 8 or 9.A potassium double salt, KUO2(S2HCNC6H11)3 · 3 H2O is described. A report is also given of the transformation of the calcium double salt on boiling with NaOH.
Résumé Le dithiocarbamate de cyclohexylsodium réagit dans le domaine de pH 6,6 à 7,2 sur les sels d'uranyle avec formation d'un complexe coloré en jaune, soluble dans l'eau, qui possède à pH 6,6 un maximum d'absorption pour 392–394 nm. Par addition de lessive alcaline jusqu'à pH 8 à 9 on décolore momentanément la solution aqueuse.On décrit un sel double de potassium KUO2(S2HCNC6H11)3 · 3 H2O; on rend compte, de plus, de la transposition du sel double de calcium par chauffage avec la soude.
Gewidmet zur 100. Wiederkehr des Geburtstages vonFriedrich Emich. 相似文献
76.
1. Historical remarks concerning magnetic influence on the polarization of resonance fluorescence and its explanation as the Zeeman effect. 2. Rotation of the plane of polarization of the resonance fluorescence of Hg by weak magnetic fields and determination of the lifetime of the excited state. 3. Experiments concerning the excitation of the resonance fluorescence of Hg by light with different kinds and directions of polarization. 相似文献
77.
Comparison between the adsorption behaviors of an organic cation and an organic anion on several reversed-phase liquid chromatography adsorbents 总被引:1,自引:0,他引:1
Adsorption data of an organic cation (propranololium chloride) and an organic anion (sodium 1-naphthalene sulfonate) were measured by frontal analysis on two RPLC adsorbents, Symmetry-C18 and XTerra-C18, with aqueous solutions of methanol as the mobile phases. The influence of supporting neutral salts on the adsorption behavior of these two ions are compared. The Henry constants are close (H approximately 5). The four sets of isotherm data are all well accounted for using the bi-Moreau model. However, the isotherms of the two ions behave differently at high concentrations. The initial behaviors of all the isotherms are antilangmuirian but remain so in a much wider concentration range for the cation than for the anion, due to its stronger adsorbate-adsorbate interactions on the low-energy adsorption sites. The retention times of both ions increase with increasing concentration of neutral salt in the mobile phase, suggesting the formation of ion-pair complexes, with Cl- for the cation and with Na+ for the anion. The adsorbate-adsorbate interactions vanish in the presence of salt and the bi-Moreau isotherm model tends toward a bi-Langmuir model. Differences in adsorption behavior are also observed between the cation and the anion when bivalent inorganic anions and cations, respectively, are dissolved in the mobile phase. High concentration band profiles of 1-naphthalene sulfonic acid are langmuirian, except in the presence of a trivalent cation, while those of propranolol are antilangmuirian under certain conditions even with uni- or divalent cations. 相似文献
78.
利用锁定放大器, 恒电势仪, 压控频率正弦波信号发生器等组装成电解池电阻和容抗的快速测定仪。可以快速地自动测是和绘出阻抗谱图和电阻/容抗~时间图。采用微小恒定振幅正弛交流电流(<10 μA)作为微扰, 数据可能较为可靠。给出了线路及所需滤波器元件的数据, 说明仪器各部份之间的干扰可以减少。测定了滴汞电极在1 mol L~(-1)Na_2SO_4溶液中及1 mol L~(-1)Na_2SO_4被正庚醇饱和的溶液中的微分电容~电势数值。证明仪器工作良好。另外, 从实验数据和理论分析, 均表明D.C.Grahame的被广泛引用的有关经典数据有误。本文做了修正。还测定了半导体氧化铁电极在光照下黑暗中的阻抗谱图和氧化银电极充电和停止充电后开路下的电阻~时间图, 显示了仪器在电化学研究中利用的可能性。 相似文献
79.
Wilhelm Geilmann 《Fresenius' Journal of Analytical Chemistry》1962,192(1):14-27
Zusammenfassung Ursprung und Entwicklung der dokimatistischen Analyse sowie die alten Verfahren der Gold-Silber-Trennung werden geschildert. Anschließend werden die klassische Lötrohranalyse sowie die Flammenreaktionen von Bunsen behandelt. Zum Schluß sind die sich auf diese alten Verfahren stützenden Fortentwicklungen der klassischen Probiermethoden erwähnt, die zu den leistungsfähigsten Bestimmungsverfahren der neuzeitlichen Analyse zu rechnen sind, wie die Bestimmung kleiner Hg-Mengen nach Stock, die mikrodokimastischen Verfahren von Haber u. Mitarb. sowie die Verdampfungsanalyse in ihren verschiedenen Anwendungen. 相似文献
80.
James O'Donnell Bruno Rusterholz Barbara Aebersold Denise Rüegg Wilhelm Simon Ernö Pretsch 《Mikrochimica acta》1994,113(1-2):45-52
In an investigation of octamethylene bis(malonic acid diamides) and their selectivities for magnesium, it was found that presence of secondary amides within the particular ionophore played a considerable role in the enhancement of magnesium selectivity. Similar effects in other ionophores, i.e. tris(malonic acid diamides), were thus systematically looked at with the help of selectivity measurements with the hope of optimizing the number of secondary and tertiary amides so as to improve the magnesium selectivity. The syntheses of several investigated tris(malonic acid diamide) isologues are equally reported.Deceased in November 1992 相似文献