Liquid-phase polymer-based retention,a new method for separation and preconcentration of elements

A method based on the retention of inorganic ions by water-soluble polymeric reagents (liquid-phase polymer-based retention) in a membrane filtration cell is suggested for the separation and preconcentration of various elements. The preseparated elements remain in the aqueous solution, which is convenient for most instrumental methods of completing the analysis. The water-soluble poly(ethyleneimine) and its thiourea and methylated derivatives are shwon to be useful for retention of different inorganic ions and their separation from elements not bound to the polymer reagent.     

Synthesis and Structures of Two Isomeric 4‐Diazo‐2,3,4,5‐tetrahydrofuran‐3‐ones

The two regioisomeric 4‐diazo‐2,3,4,5‐tetrahydrofuran‐3‐ones 6 and 7 were prepared via the common intermediate 2,3,4,5‐tetrahydro‐2,2‐dimethyl‐5,5‐diphenylfuran‐3‐one ( 8 ). Diazo transfer with 2,4,6‐triisopropylbenzenesulfonyl azide yielded 6 , whereas 7 was obtained via oxidation of the monohydrazone 12 , which was prepared selectively from tetrahydrofuran‐3,4‐dione 11 . The crystal structures of 6 and 7 have been established by X‐ray crystallography.     

Reinforced track membranes in methods for estimating the quality of natural and drinking water

Reinforced track membranes are used for the first time to study element distribution between particles of various sizes and other water components. The properties of the reinforced track membranes are considered. Factors affecting the quality of water in the Volga River in the region of the water intake of the city of Dubna in the Moscow region and potable water in various districts of the city in are characterized by the fractional composition of macro- and microcomponent.     

Synthesis of 4-fluoroalkyl-substituted pyridazines from fluorinated diazodiketones

Two approaches are reported for the preparation of 3,4,6-trisubstituted pyridazines from fluoroalkyl-containing diazodiketones: the sequence of Wittig/Staudinger/diaza-Wittig and Staudinger/Wittig/diaza-Wittig reactions. The implementation of the Wittig reaction at the first stage gives rise to considerably higher yields of the targeted pyridazines than through initial phosphazines. In both approaches the final stages of the synthesis (the formation of vinylphosphazines and the subsequent diaza-Wittig reaction) occur as a tandem process. R^F-activated carbonyls are much more reactive in Wittig olefination of diazodicarbonyl and 1,3-dioxophosphazine molecules, than non-fluorinated acyl and aroyl carbonyl groups (R^FCO ? COAlk, COAr), and as a result non-fluorinated diazodiketones and their phosphazines do not produce pyridazines under the same conditions.     

Cyclic and acyclic sulfonimides in reactions with Rh(II)-ketocarbenoids: a new access to chemoselective O-functionalization of the imidic carbonyl groups

Catalytic decomposition of diazoacetylacetone, diazoacetoacetic, diazomalonic, and diazoacetic esters using dirhodium tetraacetate in the presence of isothiazol-3(2H)-one 1,1-dioxides and a number of N-(arenesulfonyl)carboxamides in solutions of methylene chloride or dichloroethane gives rise to O-alkylation of the imidic carbonyl groups by Rh(II)-carbenoids and the formation of O-alkylimidates as the final products. The reaction proceeds with high chemoselectivity via carbonyl ylides and offers a powerful method for the synthesis in good yields of the imidates with polyfunctional O-alkyl groups. On the basis of X-ray analysis and 1H- and 13C-NMR studies it was shown that the resulting acyclic O-alkylimidates have the E-configuration in the solid state and in solution. Unlike acyclic analogues, the cyclic carbonyl ylide derived from substituted diazosaccharin by intramolecular cyclization of the appropriate diketocarbenoid is capable of reacting with DMAD in a 1,3-cycloaddition process.     

On Residual Properties of Pure Braid Groups of Closed Surfaces

We prove that pure braid groups of closed surfaces are almost-direct products of residually torsion free nilpotent groups and hence residually torsion free nilpotent. As a corollary, we prove also that braid groups on 2 strands of closed surfaces are residually nilpotent.     

Microstructural investigations of sorption layers in mass-sensitive sensors for the detection of nitrogen-containing compounds

The influence of the nature of sorption phases on the microweighing parameters of volatile organic compounds sorbed from gases and vapors is investigated using microstructural methods. The mechanism of interaction between nitrogen-containing compounds and universal polymeric and solid-phase specific sorbents is found. The roughness parameters of piezoelectric-resonator electrodes are estimated before and after the deposition of thin sorbent films and during the sorption and desorption of nitrogen-containing compound vapors. Recommendations on how to employ piezoelectric resonators with films for identifying different compounds of gas and air mixtures are presented.