Chlorine derivatives of octaorganylsilasesquioxanes

The chlorination of saturated and unsaturated octaorganylsilasesquioxanes proceeds through two pathways, leading to the formation of volatile and nonvolatile products, whose ratio depends on the reaction conditions. The volatile products of the chlorination of R-T₈ (R=C₂H₅ and CH=CH₂) are compounds with the general formula Cl_nR_8–n[SiO_1.5]₈, (n=1–7), obtained independently of the nature of the organic substituent and chlorinating agent. The nonvolatile chlorination products are silasesquioxanes, containing chlorine and chloroalkyl substituents on the atoms of the silicon-oxgyen core. Analysis of the vibrational spectral data indicated that the most significant changes in the molecular vibrational system are made by the halogenation of the silicon-oxygen core Si₈O₁₂.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 446–450, February, 1990.     

Neutron activation for precise nuclear data

Techniques for extracting neutron flux parameters pertaining to the irradiation positions and nuclear data pertaining to the isotopes concemed from measured reaction rates have been developed. An adjustment procedure based on the generalized least squares method with incorporates the, evaluated literature nuclear data, estimates of flux parameters and the experimentally measured reaction rates using high resolution -ray spectrometry is applied. More precise values of the nuclear data, i.e., thermal neutron cross sections, resonance integrals and -ray emission probabilities are thus generated. The irradiation of a multi-element standard (MES) containing 24 elements is carried out in six diffieret positions in two diverse types of reactor in the UK and Russia. It is shown that the improvement in nuclear data is revelaed in moire than 90% of the cases.     

Fission track mapping of uranium in black spruce (Picea Mariana) twigs

Fission track analysis (FTA) has been used to investigate the biological uptake of uranium. Examination of fission track maps of black spruce twigs (from areas of uranium mineralization and mill tailings) shows uranium to be concentrated in the inner bark while decreasing in the outer bark of the twigs. Track clusters in the bark, too large to be uraniferous airborne particulate matter, are identified as being associated with resin canals in the twigs. The results of this work help clarify the mechanisms by which uranium is incorporated in black spruce twigs. The observation of decreasing uranium content with the increasing age of black spruce twigs by an earlier worker, can now be explained by the relative reduction in volume of the uranium enriched inner bark with age.     

The dependence of the fatty-acid composition of cottonseed oil on the degree of unsaturation

Summary 1. Results of thiocyanometric and spectrophotometric analysis of cottonseed oil confirm the relationship found previously in catalytic hydrogenation using potentiometric monitoring of the state of the catalyst.2. Together with Eqs. (3) and (4), these results counterbalance the results of the chromatographic analysis of cottonseed oil.3. This contradiction leads to the posing of the question of the probable inaccuracy of individual methods of chromatographic analysis for substances with similar absorption properties, i.e., for linoleic and oleic acids.Alma-Ata Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 697–700, November–December, 1975.     

The interference of heteronuclear chromium(III) tartrate complexes in the EDTA titration of cobalt(II), copper(II), zinc(II) and cadmium(II)

When present together in solution, chromium(III) and tartrate can interfere seriously in the titration of Co(II), Cu(II), Zn(II) and Cd(II) with EDTA. Ternary (heteronuclear) tartrate complexes containing Cr(III) and bivalent metal ion in the ratio 1:1 are formed. The conditions for the formation of these complexes have been investigated. Cadmium(II) can be determined without interference by employing potentiometric end-point detection.     

Synthesis and oxidation of 2,6-dimethyl-3, 5-di(phenoxycarbonyl)-1,4-dihydropyridines

A number of new aryl esters of acetoacetic acid were obtained in the reaction of phenols with diketene in the presence of triethylamine. Reaction of the esters thus obtained with hexamethylenetetramine gave, for the first time, aryl esters of 1,4-dihydropyridine-3,5-dicarboxylic acid, the oxidation of which with chloranil gave the corresponding pyridines.     

Lithium determination by the nuclear track technique

Résumé On utilise la technique traceur nucléaire pour doser le lithium dans le milieu biologique étalon 1571 (Feuilles végétales). Pour déterminer la concentration en lithium on compte les traces produites dans l'acétate de cellulose par les particules alpha issues du bombardement du lithium par des neutrons thermiques:⁶Li(n, α)³H.      

Diene synthesis with 2-pyrones and 2-pyridones XIV. 1,4-Cycloadducts of 1-alkyl-2-pyridones with N-phenylmaleinimide and maleinimide

1-Alkyl-2-pyridones react with N-phenylmaleinimide and maleinimide stereoselectively via the scheme of the diene synthesis to give imides of 8-alkyl-8-azabicyclo[2.2.2]-4-octen-7-one-1,2-dioic acid. 3-Unsubstituted 2-pyridones form adducts with an endo configuration, whereas 1,3-dimethyl-2-pyridone gives an exo adduct under the same conditions. The endo- and exo-bridge adducts readily undergo retrograde diene disintegration on heating.     

Plasticized open-cell polyurethane foam as a universal matrix for organic reagents in trace element preconcentration: Part I. Collection of silver traces on dithizone foam

The preparation of plasticized foam containing dithizone or zinc dithizonate is described. The foam was used successfully for the rapid and quantitative collection of trace amounts of silver in batch and column experiments. The preconcentration of small amounts of silver from dilute aqueous solutions was found to be possible. The effects of different plasticizers, pH of the aqueous phase, and dithizone concentration in the foam, on the collection rate of silver were critically investigated.     

Possibilites et limites de l'analyse par activation neutronique multielementaire d'echantillons biologiques avec ou sans separation de la matrice activable

The possibilities and limits of the multi-elemental determinations in biological samples by neutron activation analysis with and without chemical separation are discussed.