Search results for "element"
showing 10 items of 13601 documents
1976
Electrochemical Syntheses of Carboxylic Acids from Carbon Dioxide
1987
The first report on the reduction of carbon dioxide is due to the venerable name of Hermann Kolbe, who, in 1861, published with R. Schmitt the reduction of carbon dioxide to formate with metallic potassium (1). Seven years later he introduced to the Chemical Society in London his assistant E. Drechsel, who “after many unsuccessful experiments, made during several years” (2) at the end succeeded in reducing carbon dioxide to oxalate with metallic sodium or with potassium amalgam in anhydrous conditions. Soon afterwards Beketov (3) and Royer (4) opened the series of papers dealing with the direct involvement of carbon dioxide in electrolytic processes. Since then the reduction of carbon dioxi…
Catalytic combustion of ethane over high surface area Ln1−xKxMnO3 (Ln = La, Nd) perovskites: The effect of potassium substitution
1997
Publisher Summary As a general trend, the substitution of the rare earth cation by potassium decreased the intrinsic activity, reduced the reaction order in oxygen, and, for the more substituted samples (x>0.10), it increased the selectivity to ethene. Supported platinum or palladium catalysts have so far been used almost exclusively, because of their excellent activity. However, their high price, tendency to be poisoned, and volatility in some applications have estimulated the search for suitable substitutes. LaCoO3, as a potential auto exhaust catalyst, starting a wide interest in the catalytic properties of perovskites. Their specific application as catalysts in flameless combustion has …
Aryl radicals by copper(II) oxidation of hydrazines: A new method for the oxidative and reductive arylation of alkenes
1989
Abstract A new source of aryl radicals interesting from the preparative point of view has been found in the reaction of arylhydrazines and copper(II) sulfate. The process allows selectively both the reductive and oxidative arylation of alkenes.
Tellurium(II)-Centered Dications from the Pseudohalide “Te(OTf)2”
2009
Te for two: Supported by pyridine- or carbene-based ligands, tellurium-centered dications are prepared in high yield and include a dicationic tellurium analogue of the recently synthesized "carbodicarbene". The key to accessing these compounds is the isolation of a base-stabilized form of TeOTf(2) (see structure), a new highly electrophilic reagent for tellurium chemistry.
ChemInform Abstract: A New Method for the Regioselective Synthesis of β-Enamino Acid Derivatives.
2010
Abstract A mild, simple and efficient route to β-enamino imidazole carbonilic derivatives 3 by reaction of ketimines with N,N′ -carbonyl diimidazole in the presence of boron triflouride as catalyst has been developed. The conversion of 3 to esters has also been explored.
Fluoride Complexation of Element 104, Rutherfordium (Rf), Investigated by Cation-exchange Chromatography
2008
We report on new and much more precise cation-exchange data of element 104, rutherfordium (Rf), in the fluoride ion concentration [F−] range of 5.29×10−5−1.04×10−3 M. The result based on one-atom-a...
Extraction behavior of rutherfordium into tributylphosphate from hydrochloric acid
2007
The extraction behavior of rutherfordium (Rf) into tributylphosphate (TBP) from hydrochloric acid (HCl) has been studied together with those of the lighter group-4 elements Zr and Hf. The extractability of261Rf,169Hf, and85Zr into TBP was investigated under identical conditions in 7.2–8.0 M HCl by on-line reversed-phase extraction chromatography. The percent extractions of Rf, Hf, and Zr into the TBP resin increase steeply with increasing HCl concentration, and the order of extraction is Zr > Hf ≈ Rf. By considering the order of chloride complexation among these elements, it is suggested that the stability of the TBP complex of Rf tetrachloride is lower than those of Zr and Hf.
Durch elektronenübertragung initiierte diradikalische polykombination zu linearen und cyclischen polyanionen, 1. Umsetzung des protonierten dimeren v…
1975
Die Umsetzung von 1,4-Diphenyl-1,4-bis[4-(1-phenylvinyl)phenyl]butan (1)–des protonierten Dimeren des 1,4-Bis(1-phenylvinyl)benzols (2)–mit Natrium in THF wird beschrieben und diskutiert. Die Reaktionsprodukte werden durch GPC, NMR- und Massenspektren charakterisiert. The reactions of 1,4-diphenyl-1,4-bis[4-(1-phenylvinyl)phenyl]butane (1)—the protonized dimer of 1,4-bis(1-phenylvinyl)benzene (2)—with sodium in THF is described and discussed. The reaction products are characterized by GPC, NMR, and mass spectra.
Die unter dem einfluß geringer mengen an natriumionen verlaufende schmelzkondensation von 2.6-dihydroxymethyl-4-methylphenol
1970
Die wahrend der bei 130°C verlaufenden Schmelzkondensation von 2.6-Dihydroxy-methyl-4-methylphenol (I) bestimmten Gewichtsverluste und Mengen von abgespaltenem Formaldehyd waren um so groser, je hoher der analytische Natriumgehalt der Verbindung lag; dieser wurde durch Beimischen des Natriumphenolats von I im Bereich von 0,01 bis 3,0 Gew.-% Natrium eingestellt. Die in der Literatur angegebenen, stark voneinander abweichenden Mengen von abgespaltenem Formaldehyd sind wahrscheinlich durch unkontrollierte Natriumgehalte von I bedingt; sie konnen aus dem Natriumsalz stammen, uber das Verbindung I gewohnlich hergestellt wird. The losses in weight and the amounts of formaldehyde split off, which …