Vibronic intensity borrowing. Deuterium effect and emission—absorption asymmetry of the S1---S0 transition in pyrene

The intensities of the vibrationally induced bands in the S₁---S₀ emission and absorption spectra of pyrene-h₁₀ and -d₁₀ are measured and analysed. Several new expressions are reported which relate the deuterium effect and emission—absorption asymmetry of induced spectra to the vibronic coupling mechanism.     

Étude thermodynamique de la complexation de `l'argent par la pipérazine et quelques-uns de ses dérivés en milieu aqueux

The stability constants of the complexes formed by Ag⁺ ion with piperazine and its 2-methyl-, N-methyl-, and N-phenyl-derivatives were determined in aqueous 0.1 M KNO₃ solution at 25°C, by means of the corresponding metal—complex electrodes.The direct calorimetric study of these reactions in the same conditions of temperature and medium made it possible to calculate the standard enthalpies and standard entropies of formation of the complexes.On the basis of a comparison of all the thermodynamic functions of these systems, the ability of each ligand to coordinate is discussed.     

Vilsmeier formylation of 2-methyl-3 -carbethoxy-5-methoxy- and 2-methyl-5-methoxyindoles

The corresponding 6- and 3-formyl derivatives were obtained by formylation of 2-methyl-3-carbethoxy-5-methoxy- and 2-methyl-5-methoxyindole derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 339–341, March, 1971.     

Adsorption indicators in the titrations of hexacyanoferrate(II) and oxalate with thorium ions

Alizarin Red S, Pyrocatechol Violet and Xylenol Orange are shown to be effective adsorption indicators for the titrations of hexacyanoferrate(II) and oxalate with Thorium(IV) solution. The action of the indicators can be explained by the theory of surface compound formation.     

Radiometrische schnellbestimmungen mit ädte durch rückmessung

The principle of back-titration with EDTA is applied to rapid radiometric methods. A suitable vessel for performing the reaction, filtration and count-rate measurement is described. The optimal conditions for the use of solid ^110mAgIO₃ as indicator were studied: the time for solubility-equilibrium of solid silver iodate, the reaction time of EDTA with silver iodate, and the pH-dependence of the silver-EDTA reaction rate. Procedures are given for calibration curves and for rapid radiometric determinations of copper(II). nickel(II), lead(II) and zinc(II). The method is suitable for the range 1–100μg.     

Pregnane glycosides of Cynanchum sibiricum III. The structure of sibiricosides D and E

Summary The structures of two pregnane glycosides fromCynanchum sibiricum Willd. have been established. Sibiricoside D (II) is sibirigenin (cynanchogenin) 3-D-glucosido-D-cymarosido-D-cymarosido-D-cymarosido-D-oleandroside. Sibiricoside E (I) is sibirigenin (or cynanchogenin) 3-D-glucosido-D-glucosido-D-cymarosido-D-cymarosido-D-cymarosido-D-oleandroside.The hypothesis has been put forward that glycosides of isolinoleone are present in the native state which are isomerized into linoleone derivatives in the process of isolation and treatment with acid and alkaline agents.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 171–177, March–April, 1975.     

The reactive states of ions: Octatrienes and dimethyl substituted cyclohexadienes

The principal decomposition routes of molecular ions of cis, cis, cis-2,4,6-octatriene, cis, cis, trans-2,4,6-octatriene, trans, cis, trans-2,4,6-octatriene, trans-5,6-dimethyl-1,3-cyclohexadiene and cis-5,6-dimethyl-1,3-cyclohexadiene were studied using ion kinetic spectroscopy. The loss of radicals from [M]⁺· appears to proceed via a ground state, while loss of a neutral molecule appears to involve either complete equilibration of structure within the system or both ground state and excited state pathways.     

Eine neue Verbindung der Zusammensetzung 9 BaNiO2·2 BaCO3

Zusammenfassung Bei der Reaktion von BaCO₃ mit NiO bildet sich unter bestimmten Bedingungen ein kristallines Pulver der Zusammensetzung 9 BaNiO₂ · 2 BaCO₃. Die Verbindung zeigt scharfe Röntgeninterferenzen, die sich kubisch indizieren lassen. Es wurden elektronenmikroskopische Aufnahmen gemacht sowie Elektronenstrahlfeinbereichsbeugungen durchgeführt. Das IR-Spektrum wurde aufgenommen und die magnetische Suszeptibilität bestimmt.

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A new compound 9 BaNiO₂·2 BaCO₃

During the reaction of BaCO₃ with NiO under special conditions a crystalline powder with the composition 9 BaNiO₂ · 2 BaCO₃ is formed. This compound shows clear X-ray patterns which can be indexed using a cubic cell. Electron microscopic investigations have been carried out and selected area diffraction patterns have been taken. The IR-spectrum and the magnetic susceptibility have been proved.

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Zdanovskii’s Rule and Isopiestic Measurements Applied to Synthetic Bayer Liquors

Isopiestic measurements of mixed electrolyte solutions involving sodium hydroxide and other components of Bayer liquors were performed at 50?°C and 100?°C. Most of the systems studied obey Zdanovskii’s rule exactly or very closely. However, those with sodium chloride as one of their components show deviations from Zdanovskii’s rule, which are well predicted by our thermodynamic modelling software based on Pitzer’s equations.     

Spectroscopic investigations in molecularly organized solvent media. Part 3. Examination of the nitromethane selective quenching rule in aqueous anionic + cationic and anionic + nonionic mixed surfactant solutions

Applicability of the nitromethane selective quenching rule for discriminating between alternant versus nonalternant polycyclic aromatic hydrocarbons (PAHs) is examined for 20 representative PAH solutes dissolved in micellar sodium dodecylsulfate (SDS) + cetyltrimethylammonium bromide (CTAB), SDS + dodecyltrimethylammonium bromide (DTAB), SDS + Brij-35, and SDS + sodium octanoate (SO) mixed surfactant solvent media. Experimental results show that nitromethane quenched fluorescence of all 8 alternant PAHs studied in the four different solvent systems. Unexpected quenching behavior was observed, however, in the case of nonalternant PAHs. Nitromethane quenched fluorescence emission of nonalternant PAHs dissolved in the SDS + SO solvent media, which is contrary to the selective quenching rule. In the case of the mixed anionic + cationic surfactant solvent media, nitromethane quenching selectivity was restored at concentration ratios of approximately 4 : 1 (anionic:cationic) or less. Received: 22 May 1997 / Revised: 29 September 1997 / Accepted: 3 October 1997