Titrimetrische Bestimmung von Zink mit Äthylendiamintetraessigsäure in Gegenwart von Palladium(II)

Zusammenfassung Komplexometrische Methoden zur Bestimmung von Zink in Gegenwart von Palladium(II) wurden ausgearbeitet. Dabei wird Palladium(II) mit Kaliumcyanid getarnt und der Zinkgehalt entweder bei p_H 5,8 oder nach Demaskierung mit Chloralhydrat bei p_H 10 mit ÄDTA gegen Methylthymolblau titriert. Diese Zinkbestimmung läßt sich auch in Anwesenheit einer Mischung von Palladium(II), Kupfer(II), Nickel und Kobalt(II) durchführen.

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Summary Complexometric methods have been developed for determining zinc in the presence of palladium(II). In these procedures, Pa(II) is masked with potassium cyanide and the zinc content is titrated either at p_H 5.8 or after demasking with chloralhydrate is titrated with EDTA at p_H 10 in the presence of methylthymol blue. This zinc determination may also be conducted in the presence of a mixture of palladium(II), copper(II), nickel(II),and cobalt(II).

     

Aufbau und Zunderverhalten von Niob-Bor-Silicium-Legierungen

Zusammenfassung Der Aufbau des Dreistoffes Niob-Bor-Silicium wird bei 1600° C mit Hilfe röntgenographischer und mikroskopischer Methoden ermittelt. Die T 2-Phase sowie die ternäre D 8₈-Phase besitzen einen ausgedehnten homogenen Bereich. Während Silicium in T 2 durch Bor bis annähernd Nb₅SiB₂ substituiert wird, besteht beim D 8₈-Typ eine Gitterauffüllung gemäß Nb₅Si₃B. Oxydationsversuche im Bereich von 400 bis 1200° C zeigen vor allem die Selektivität, indem Nb–Mk bzw. die Nb-Boride bevorzugt in Pentoxyd übergehen. Silicium übt einen stabilisierenden Einfluß auch auf das Bestehen von -Nb₂O₅ aus. -Nb₂O₅ tritt als Mischphase mit Anionendefekt auf, wodurch die sogenannte scharfe und diffuse Form erklärt wird. Die Umwandlungstemperatur - wird teilweise erheblich oberhalb der vonGoldschmidt angegebenen beobachtet. Die -Form wird als M-Modifikation nachBrauer identifiziert und relativ häufig nachgewiesen. Die -Form erweist sich alsBrauersche H-Modifikation und entsteht offensichtlich stufenweise (fast kontinuierlich) aus -Nb-Oxyd. Auf die Anionendefekt-Bildung wird nachdrücklich hingewiesen.Mit 3 Abbildungen     

Synthesis and conversions of metallocycles. 7. A novel approach to the synthesis of 3,4-dialkyl-substituted aluminacyclopentanes in the presence of Cp2ZrCl2

A novel approach was developed for the stereoselective synthesis of trans-3,4-dialkyl-substituted aluminacyclopentanes from -olefins, metallic magnesium, and EtAlCl₂ in the presence of catalytic amounts of Cp₂ZrCl₂. The hydrolysis and deuterolysis products of the 3,4-dialkyl-substituted aluminacyclopentanes obtained are only in the trans configuration.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1607–1609, July, 1991.     

2,3-Diphenylthiazolo[3,2-a]pyrimidinium salts

The corresponding 2,3-diphenyl[3,2-a]pyrimidinium salts were obtained by the condensation of 4,5-diphenyl-2-aminothiazole perchlorate with -diketones, -chlorovinyl ketones, -chlorovinyl aldehydes, and 1,1,3,3-tetraethoxypropane. The PMR spectra were used to prove the structures of the compounds obtained, particularly to select the structures of the isomeric salts obtained in the condensation with unsymmetrical -diketones, -chlorovinyl ketones, and -chlorovinyl aldehydes. As a rule, the latter give one isomer — the -unsubstituted (relative to the bridge nitrogen atom) derivative.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 629–631, May, 1972.     

Catalytic properties of iron tetracarbonyl π-complexes of vinylsilanes in the addition of polyhalomethanes and hydrosilanes to vinylsilanes

Conclusions The high catalytic activity of (CH₂=CHSiR₃)·Fe(CO)₄ complexes was demonstrated in the reaction of vinylsilanes with polyhalomethanes and hydrosilanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 914–920, April, 1982.     

THE QUANTUM EFFICIENCY FOR THE INTERPHOTOCONVERSION OF THE BLUE and PINK FORMS OF PURPLE MEMBRANE

When the cations bound to purple membrane are removed it turns blue, and when this blue membrane is irradiated its color changes to pink. Irradiation of pink membrane leads to the reformation of blue membrane. We have determined that the quantum efficiency for the formation of pink membrane from deionized blue membrane is 1.6 ± 0.6 ± 10 ⁴ at 0^oC, pH 5.0. We also found that the quantum efficiency for the back photoconversion, i.e. the formation of blue membrane from pink membrane, is 8.8 ± 1.6 ± 10^-3 at 0^oC, 55 times greater than that of the forward photoconversion reaction. The extinction coefficients of the pink membrane and blue membrane were determined to be 44 500 ± 670 cm^-1 M^-1 at 491 nm and 54 760 ± 830 cm^-1 M ^-1 at 603 nm, respectively, assuming light-adapted purple membrane is 63 000 cm^-1 M ^-1 at 568 nm. The quantum efficiency for forming pink membrane from blue membrane is much lower than that for forming the photointermediate of the blue membrane's photocycle. Their relationship is similar to that of light-adaptation and photocycle of the dark-adapted purple membrane.     

The synthesis of 1,4-diazacycl[3,2,2]azine

The diazaanalog of “cycl[3,2,2]azine”, “1,4-diazacycl[3,2,2]azine” (1,4,7b-triazacyclopent-[cd]indene) and its 2-methyl derivative were prepared. These compounds are subject to facile acid-catalyzed hydrolysis affording substituted imidazo[1,2-a]pyridines.     

Structure of the products of the cyclization in acetic anhydride of β-(2-carboxy-5-chlorophenylamino) propionic acid and its nitrile

-(2-Carboxy-5-chlorophenylamino)propionic acid cyclizes in acetic anhydride to form 4-chloro-2-(2,4-dioxopiperidino)benzoic acid, which subsequently undergoes conversion into its lactone. Under the same conditions, -[acetyl(2-carboxy-5-chlorophenyl)amino]-propionitrile forms 7-chloro-1--cyanoethyl-1,2,3,4-tetrahydroquinoline-2,4-dione. The structures of the compounds obtained were confirmed by their IR, UV, and PMR spectra. An evaluation of the stability of the ketonic and enolic forms of the compounds obtained on the basis of calculations by Hückel's method has been made.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 7, pp. 879–884, July, 1970.