Free energies of transfer of alkali halides from water to urea-water mixtures at 25°C from EMF measurements

The standard potentials_s E ^o of M/M⁺ (M=Li, Na, K, Rb, and Cs) electrodes in aqueous urea solutions containing 12, 20, 30 and 37% by weight of urea have been determined at 25°C from emf measurements on the cell M(Hg)/MCl (m), solvent/AgCl–Ag, from the activities of metals in amalgams by use of a similar type of cell in water, and from the values of_s E ^o of the Ag/AgCl electrode determined earlier. The standard free energies of transfer of MCl, G _t ^o (MCl), from water to the mixed solvents, computed by use of these values and those for the Ag–AgCl electrode, rise sharply from Li⁺ to Na⁺ but fall from Na⁺ to K⁺ and rather sharply from K⁺ to Cs⁺ with a maximum at Na⁺ in all the solvent compositions. This has been attributed to the superimposition of soft-soft interactions on the electrostatic interactions between the ions and the negative charge centers of the possible hydrogen-bonded solvent complexes in the mixed solvents. Comparison of G _t ^o (i) values for individual ions, obtained by a simultaneous extrapolation procedure, with those in aqueous mixtures of methanol,t-butanol, and dimethyl sulfoxide leads to the conclusion that the solvation of these ions in all these solvents is chiefly dictated by the acid-base type of ion-solvent interactions.     

Facile Synthesis of Tricyclic 1,2,4-Oxadiazolines-Fused Tetrahydro-Isoquinolines from Oxime Chlorides with 3,4-Dihydroisoquinoline Imines

A mild and efficient strategy for the synthesis of tricyclic 1,2,4-oxadiazolines-fused tetrahydro-isoquinolines derivatives via [3 + 2] cycloaddition reaction is reported. The reactions provided the functionalized tricyclic 1,2,4-oxadiazolines in high yields (up to 96%). This protocol is simple and easy to handle. Moreover, a gram-scale experiment further highlights the synthetic utility. The chemical structure of the product was determined by X-ray single-crystal structure analysis. A possible mechanism for this transformation is proposed to explain the reaction process.     

An optimized divergent synthesis of sulfonimide-based dendrimers achieving the fifth generation

Abstract

A novel two-step amine persulfonylation method described here results in significantly higher yields of sulfonimide-based dendrimers as compared with formerly available procedures. This allowed the preparation of the fifth-generation sulfonimide-based dendrimer for the first time, on a 2?g scale. Dendrimers of fourth and fifth generations decorated with naphthyl groups after being spin-coated on a glass substrate were shown to form stable hydrophobic films as revealed by contact angle measurements.     

Изотопные мишени для ядерных исследований

A non-contact measuring method on electrostatic potential by using α-ray ionization is proposed. In this method potential of a charged material is estimated from ionic current flowing through an ion collector attached with a small ²⁴¹Am source. As hade electrode surrounding the collector has a function of adjusting sensitivity and potential up to 50 kV was measured with precision of 1 kV.     

Untersuchungen zum Verhalten der Pt-Metalle gegenüber festen und flüssigen Kationenaustauschern mit Hilfe der Radiotracermethode

Mit Hilfe radioaktiver Nuklide wurde die Aufnahme der Pt-Metalle aus chloridhaltigen Lösungen sowoht durch feste (Wofatit KPS) als auch durch flüssige Kationenaustauscher (Bis-2-äthylhexylphosphorsäure) bei Variation des pH-Wertes, der Vorbehandlung sowie der Edelmetallkonzentration bestimmt. Pt und Ir wurden nur geringfügig, Pd und Rh dagegen deutlich stärker adsorbiert. Beide Austauschertypen zeigten qualitativ das gleiche Verhalten. Die gefundenen Abhängigkeiten der Adsorption wurden auf das komplexchemische Verhalten der Pt-Metalle zurückgeführt. Es werden Verfahren zur schnellen radiochemischen Reinigung der benutzten Nuklide angegeben.     

Efficient and Convenient Method for the Synthesis of N‐Arylhydrazones using a Palladium‐Catalyzed Bond‐Forming Reaction

A highly effective, convenient, and reproducible industrial process for palladium‐catalyzed carbon–nitrogen cross coupling has been developed and applied on a large scale. Thus various functionalized N‐arylhydrazones have been easily prepared and well characterized by conventional spectroscopic methods.     

Reaction of Epichlorohydrin with 2-Aminobenzothiazole and Its Derivatives

We have shown that 2-aminobenzothiazoles when reacted with epichlorohydrin form 3-hydroxytetrahydropyrimido[2,1-b]benzothiazolium chlorides, while 2-iminobenzothiazolines form 2-(-chloro--hydroxypropyl)iminobenzothiazolines.     

Thermal Analysis of Hexachloroplumbate and Chlorides Containing Complex Divalent Lead 2,2'-bipyridine Cations

Lead(II) 2,2'-bipyridine hexachloroplumba tetetrahydrate was synthesized and investigated by DTA, TG and DTG. IR spectroscopy and other methods enabled the identification of some of the decomposition products. Comparative studies on the corresponding chlorides: [Pb(bipy)]Cl₂ and [Pb(bipy)₃]Cl₂, which can be considered as precursors of the hexachloroplumbate, were also undertaken. X-ray measurements enabled the tentative determination of the crystal structure of [Pb(bipy)]Cl₂. Hexachloroplumbate decomposes with the liberation of chlorine, water and organic ligands, and the process is accompanied by the simultaneous transition of Pb(IV)→Pb(II). Chlorides release only ligands upon heating. Residues comprised always PbCl₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

Heterometallic zirconocene(iii) aluminum hydride complex (Cp2ZrH)2HAlCl2·C4H8O2·C6H6

The heterometallic zirconocene(iii) aluminum hydride complex (Cp₂ZrH)₂HAlCl₂·C₄H₈O₂·C₆H₆ was synthesized by reduction of Cp₂ZrCl₂ with lithium aluminum hydride in the presence of Cp₂TiBH₄ and 1,4-dioxane, and its structure was established by X-ray diffraction analysis.     

Efficient synthesis of chalcone-4′-sulfonyl chlorides and fluorides

A library of 4′-chloro- and 4′-fluorosulfonyl-substituted chalcones was prepared via the aldol-type condensation reactions of 4-acetylbenzene-1-sulfonyl halides with various aromatic aldehydes, either in absolute ethanol or glacial acetic acid, in the presence of dry HCl. This represents the first examples of chalcone sulfonyl halides in which the phenone ring bears one of these functional groups. The reactivity of the chalcone sulfonyl halides were strongly dependent on the styrene ring substituents; sulfonyl chlorides reacted with most nucleophiles (e.g. amines, alcohols), while sulfonyl fluorides reacted only with charged nucleophiles (e.g. phenolates).