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21.
A method is described for the gas-chromatographic determination of the diastereomers of vitamin K1 (phylloquinone) in the form of their dihydro dimethyl ethers. The reported method of derivatization and chromatographic analysis in conjunction with optical rotation measurements are useful approaches for characterization of vitamin K1 samples with respect to their origin. 相似文献
22.
Reactions of π-Organonickel Complexes with Tertiary Phosphanes In a hexane solution Ni(C5H5)2 reacts with PBu3 or Ph2PBu forming the nickel(O) complexes Ni(PBu3)4 or Ni(Ph2PBu)4 (A). Under the same conditions only one cyclopentadienyl ligand is substituted by PhPBu2 and the nickel(I) compound (C5H5)Ni (PhPBu2)2 (B) is obtained. Products of the reactions between B and α,α′-dipyridyl, hydrogen chlorid in ether, or Ni(PhPBu2),Cl2 are Ni(dipy)2, [PhPHBu2]2[NiCl4], or (C5H5) Ni(PhPBu2)2Cl. By the reaction with HgCl2 a cyclopentadienyl compound of an unknown structur is formed. The compound Ni(PhPBu2)4 which is analogous to A is synthesized by the reduction of bis(acety1acetonato)-nickel with Et2AlOEt in the presence of PhPBu2 or by the reaction of bis (cyclooctadiene-1,5)-nickel with PhPBu2. 相似文献
23.
Chiral salicylidenphenethylamines (R)‐HA or (S)‐HA , 2‐salicylidenfurfuryl‐imines HB , and 2‐salicylidenaminoethanol HC react with sodium hydride or sodium hexamethyldisilylamide to form the sodium complexes [Na(R)‐A] 4 · 0,5 Et 2 , [Na(S)‐A] 4 · 0,5 Et 2 O (1) , [NaB] 4 · 0,5 Ph‐Me (2) and [(dme)NaC] 4 (3) . In the presence of 18‐crown‐6 the complex [Na(18‐crown‐6)(thf) 2 ] 2 [Na 2 (C)] 4 · THF (4) can also be isolated. The crystal structure analyses of both 1 and 2 show that heterocubane structures with a Na4O4 frame work are formed. Additionally, the imine nitrogen atom is bonded at the Na atom which has the coordination number 4 in 1 . Additional coordination of the furfuryl oxygen atom results in the coordination number five for the sodium atom in 2 . In 3 which is also a tetramer, two Na2O2 units are connected via two imino‐ethanol bridges Na(1)‐N(=CH‐phenolat)‐CH2CH2‐OH‐Na(2A). The crystal structure analysis displays that 4 is an ionic compound consisting of two [(thf)2Na(18‐crown‐6)]+ cations and the dinuclear dianion [Na 2 (C) 4 ] 2? . Both 1 and 2 are carboxylation reagents which transfer CO2 to 2‐fluoropropiophenone. 1 is more active than 2 , but 3 and 4 are inactive. 相似文献
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The mass spectra of the pyrrolidides of some long-chain carboxylic acids with alicyclic residues attached to their ω-end are discussed and compared with the spectra of the corresponding esters. Fragmentation triggered by the pyrrolidide group generates a series of peaks, which clearly exhibits the size and the structure of the carbon chain. 相似文献
27.
One-atom maser 总被引:2,自引:0,他引:2
28.
Walther Lamprecht und Hubert Katzlmeier 《Fresenius' Journal of Analytical Chemistry》1961,181(1):216-229
Zusammenfassung An kristallisierten Enzymen des biologischen Stoffwechsel wird gezeigt, daß bei der Polarographie nur die schwefelhaltigen Proteine katalytische Wasserstoffwellen geben. Von den in der Literatur beschriebenen Doppelstufen der Proteine besitzt nur die im negativeren Potentialbereich liegende Welle die eigentliche katalytische Funktion. Die erste Vorwelle von Proteinen verschwindet, wenn die polarographische Messung bei 0° C durchgeführt wird.In Proteinen sind nur Disulfidgruppen katalytisch wirksam. Sogenannte reine Sulfhydryl-Enzyme haben keinen katalytischen Effekt. Typische SH-Enzyme können jedoch polarographisch als p-Chloromercuribenzoatkomplexe gemessen werden.Durch Harnstoffzusatz bei der polarographischen Messung von Proteinen gelingt es, zwischen maskierten und freien Sulfhydryl- oder Disulfidgruppen an Enzymen zu definieren.Auszug aus der Dissertationsschrift H. Katzlmeier, Technische Hochschule München (1959). 相似文献
29.
Favero LB Giuliano BM Melandri S Maris A Ottaviani P Velino B Caminati W 《The journal of physical chemistry. A》2005,109(33):7402-7404
The molecular beam Fourier transform microwave spectrum of 1,4-dioxane-trifluoromethane has been assigned and measured. The two subunits form a cage stabilized by one C-H...O and two C-H...F weak hydrogen bonds. The C-H...O link involves the axial lone pair of one of the two equivalent ring oxygens, while the two C-H...F bridges connect trifluoromethane to the two axial hydrogens in positions 3 and 5. The dissociation energy has been estimated from the D(J) centrifugal distortion parameter to be approximately 6.8 kJ/mol. 相似文献
30.
Ternary Thallium Indium Sulfides: A Summary Combined thermal and X-Ray analyses in the ternary system Thallium—Indium—Sulfur show, that the two binary sections Tl2S? In2S3 and TlS? InS contain ternary compounds with unique crystal structures. The chemical formulas of these ternary solids are TlIn5S8, TlIn3S5, TlInS2 and Tl3InS3 for the section Tl2S? In2S3 and TlIn5S6 as well as Tl3In5S8 (metastable high temperature phase) for the section TlS? InS respectively. With TlIn5S7 an additional ternary solid could be detected, which is located outside the two sections. It is derived from the binary mixed valence compound In6S7 by complete substitution of In+ by Tl+. The following ionic formulations make the mixed valence character of the ternary Thallium—Indium-Sulfides reasonable: TlIn5S8 = Tl+(In3+)5(S2?)8, TlIn3S5 = Tl+ (In3+)3(S2?)5, TlInS2 = Tl+In3+(S2?)2, Tl3InS3 = (Tl+)3In3+ · (S2?)3, TlIn5S6 = Tl+([In2]4+)2In3+ (S2?)6, Tl3In5S8 = 4 × [(Tl+)0,75 · (In+)0,25In3+(S2?)2], TlIn5S7 = Tl+[In2]4+ (In3+)3(S2?)7. All compounds contain Tl+-ions in a characteristic “lone pair coordination” of S2? ions. Indium atoms however occur with the oxidation numbers +2 (formal, In2 dumb bells with covalent In? In bonding) and +3 (with In3+ in tetrahedral and octahedral coordination of S2?). Chemical preparation, crystal chemistry and general properties of the ternary solids are discussed, summarized and compared to each other. 相似文献