Pre-resonance Raman intensity studies of TCNQ and TCNQ−

Pre-resonance Raman spectra have been obtained for TCNQ and LiTCNQ in acetonitrile solution using an Ar⁺—Kr⁺ laser and a tunable rhodamine 6G dye laser. Using the theory of Albrecht and Hutley, we have calculated frequency factors for the intensity variations for several symmetric vibrational modes of each molecule. The observed spectra for TCNQ and LiTCNQ with violet, blue, and green excitation give evidence for B-type resonance enhancement due to vibronic mixing between at least two violet and ultraviolet transitions. The Raman spectra for LiTCNQ with yellow, orange, and red excitation show A-type enhancement due to a single electronic excitation in the near infrared.     

Zur Kenntnis des Phosphatstoffwechsels der Hefe

Scheinbare Divergenzen zwischen den seinerzeit aufgestellten Phosphatbilanzen in Säureextrakten aus phosphatangereicherter und-verarmter Hefe und den in der letzten Mitteilung dieser Reihe erhobenen Befunden über den Gehalt an freien Nucleotiden in demselben Material, veranlaßten eine genauere Überprüfung der Frage, inwieweit die Extraktionsmethoden die Ergebnisse der Nucleotidbestimmung und der Phosphatbilanzen beeinflussen. Es zeigte sich, daß bei Bestimmung der freien Nucleotide, trotz Verwendung verschiedener Extraktionsmittel, sowohl qualitativ als auch quantitativ weitgehend entsprechende Ergebnisse erhalten wurden.Die Resultate können wieder in dem Sinne erklärt werden, daß während der Phosphatanreicherung eine Synthese von Nucleinsäure auf Kosten der freien Nucleotide erfolgt.Gleichzeitig durchgeführte Phosphatbilanzen in den Säureextrakten aus phosphat-verarmter und-angereicherter Hefe ergaben je nach den Extraktionsbedingungen starke, zur Zeit noch schwer deutbare Konzentrationsunterschiede in den einzelnen Phosphatfraktionen.

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Mit 2 Abbildungen     

On the chemistry of flavin-dependent oxygen activation III. synthesis of 1.10a-dihydroflavin and its 10.10-aring opened derivative as model chromophores for enzyme-bound intermediates

Model chromophores of 1.10-dihydroflavin and its 10.10a-ring opened derivative have been isolated. By comparison with enzymatic intermediates, reaction mechanisms of flavin-dependent oxygenase and luciferase are discussed in terms of chemical structure.     

Étude thermodynamique de la complexation des lanthanides trivalents avec l'acide hydroxyethyl-ethylenediaminetriacetique et d'autres acides aminoacetiques: III. Détermination des Constantes de Formation des Complexes Mixtes par Titrage Potentiométrique

A thermodyrmmic study of the complex formation of trivaient lanthanides with hydroxyethylethyienediaminetriacetic acid and other aminoacetic acids. Part III. The determination of the formation constants of mixed complexes by potentiometric titration.The partial stability constants of the mixed and 1:2 complexes Ln—HEDTA—L (where Ln = La, Ce,... and L = glycine, IMDA, NTA, HEDTA and EDTA) have been determined by potentiometric titration at 25°C and at a constant ionic strength of 1 (KCl). The changes in stability of the complexes studied (1:1, 1:2, mixed, protonated and unprotonated) vs. atomic number of the lanthanide are discussed. The changes observed in the trends of the partial and overall stability constants across the lanthanide series are attributed to the decrease in the number of water molecules in the 1:1 LnHEDTA ·xH₂O from x = 3 for light lanthanides to x = 2 for heavy ones. However, in this 1:1 complex, HEDTA seems to be a hexadeutate ligand in the La—Sm range of the series and a pentadentate ligand in the Gd—Lu range. Significant differences have been found between the complexes containing four nitrogen atoms, i.e. L = HEDTA, EDTA, and those with three nitrogen atoms i.e. L = glycine, IMDA, NTA.     

Synthesis of 1,4-dihydropyridines having an N-alkylpyridinium substituent at the 4-position and their affinity towards liposomal membranes

There has been synthesized a series of 1,4-dihydropyridines having an N-alkylpyridinium substituent at position 4 with a varying length of hydrocarbon chain. Their affinity to model (liposomal) membranes has been studied. It was found that this affinity increased with lengthening of the hydrocarbon chain on the Npyridinium substituent at the 4-position of the 1,4-dihydropyridine ring. However, lengthening of the hydrocarbon chain in the 3,5-ester groups of the 1, 4-dihydropyridine ring led to a decrease in the binding to the liposome when a 4-(N-hexadecylpyridinium) substituent was present.Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1112–1117, August, 1995. Original article submitted June 6, 1995.     

Solvent extraction for cleaning phosphoric acid in fertilizer production

Phosphorites of sedimentary origin utilized in manufacturing of fertilizer contain uranium, thorium and products of their radioactive decay, as well as health-endangering compounds of cadmium, arsenic and fluorides. Some of them may transit into the phosphoric acid, when breaking down the phosphorites with sulphuric, acid, and then into the fertilizer. The purpose of the phosphoric acid cleaning is its decontamination from uranium and thorium as well as the removal of toxic cadmium. The above task can be achieved by solvent extraction. The paper presents the results of the extraction of uranium and cadmium from phosphoric acid using polyalkyl phosphasene and trioctyl amine, respectively. The extraction kinetics, equilibrium distribution of uranium and cadmium within the phases, the effect of extractant concentrations and temperature of the process is also discussed. The technological schemes for cleaning phosphoric acid from uranium and cadmium are given.     

Synthesis of N-benzyloxycarbonyl-N-methylaminoacids from oxazolidine-5-one derivatives

Hydrogenolysis of 3-benzyloxycarbonyloxazolidine-5-one and 3-benzyloxycarbonyl-4-benzyloxazolidine-5-one by Et₃SiH in the presence of F₃.CCO₂H is demonstrated to be a convenient method for preparing substituted N-methylaminoacids. In contrast with catalytic hydrogenation on Pd/C catalyst, the benzyloxycarbonyl is not removed and the methyl is not lost using this method.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 681–683, May, 1992.     

Complex study of nickel skeleton catalysts: V. Study of novel non-pyrophoric nickel skeleton catalysts by derivatograph

The structure and properties of non-pyrophoric skeleton catalysts prepared from NiSi, NiAlSi, NiMg and NiZn alloys have been studied—apart from other thermal methods—by means of the derivatograph.Our experimental results have contributed to the explanation of the non-pyrophoric behaviour of these catalysts. We demonstrated that the desorption of the hydrogen content in our catalysts is not accompanied by the oxidation of active nickel. This oxidation takes place only at higher temperatures, above 200°C, at a rate proportional to the amount of active nickel.Other constituents of the catalysts (adsorbed water, hydroxide content) were also determined from the experimental data. The outstandingly high Mg(OH)₂ content of the NiMg catalyst indicates that its structure is dissimilar: Mg(OH)₂ also acts as support for the catalyst.     

Quantitative Auswertung von Dünnschicht-Chromatogrammen: On line-Kopplung mit programmierbaren elektronischen Tischrechnern

Reprocessing of spherical THTR fuel elements shall be tested in the Jülich pilot plant JUPITER. This fuel type differs significantly from other fuel elements with respect to shape, composition and fissile material content. It requests special provisions for reprocessing and the necessary material balancing and safeguarding. Two material balance areas (MBA) are defined: head end and chemical extraction process. Within the 1. MBA uranium and thorium are balanced mainly by using a combination of digital counting of the fuel spheres, gammaspectrometric burn-up determination of individual spheres and X-ray fluorescence determination of uranium and thorium in nitric acid solutions which have been obtained by dissolution in Thorex reagent of the heavy metal oxides after burning of the graphite matrix. The 2. MBA begins with the solution for the chemical extraction process, collected in the so called accountability tank. After extraction according to the Thorex flowsheet the process streams are monitored in line for process control, and off line for material balancing and safeguarding. This is performed mainly by X-ray fluorescence analysis, potentiometric titrations, alpha- and mass spectrometry.