Search results for "element"
showing 10 items of 13601 documents
ChemInform Abstract: Electrical Breakdown and Pitting in Anodic Films on Tungsten in Halogen Ion-Containing Solutions.
1988
Abstract The systematic investigation of the anodic behaviour of W in halogen ion-containing solutions reveals noticeable differences in the presence of different anions. Strong generalized dissolution is observed in fluoride solutions, the oxide growth being hindered at low anodizing current densities. Sparking phenomena occur in the presence of Br− and I− anions as in nitrate and sulphate solutions. Only in Cl− containing solutions is the growth of the anodic films limited by the occurrence of pitting phenomena at a critical thickness of the oxide. The laws of dependence of the phenomenon on the experimental parameters and the influence of ferrous ions on the voltage at which pitting occu…
ChemInform Abstract: One-Pot Synthesis of Pyrrole-2-carboxylates and -carboxamides via an Electrocyclization/Oxidation Sequence.
2015
An electrocyclic ring closure is the key step of an efficient one-pot method for the synthesis of pyrrole-2-carboxylates and -carboxamides from chalcones and glycine esters or amides. The 3,4-dihydro-2H-pyrrole intermediates generated in situ are oxidized to the corresponding pyrroles by stoichiometric oxidants or by catalytic copper(II) and air in moderate to high yields. A wide range of functional groups are tolerated, and further combination with an in situ bromination gives access to polyfunctional pyrrole scaffolds.
ChemInform Abstract: Synthesis, Structure, and Properties of BaVO2(AsO4): A New Vanadium Arsenate Containing the V2O2+4 Core.
2010
An electrochemically synthesized nanoporous copper microsensor for highly sensitive and selective determination of glyphosate
2020
Calix Crowns Derived from para-Bridged Calix[4]arenes
2000
Two calix[4]arenes, bridged by aliphatic chains of five and eight carbon atoms spanning two opposite para positions, have been converted into their 1,3-crown ether derivatives by reaction with tetraethylene and pentaethylene glycol ditosylates. Of the two possible 1,3-crown derivatives, only the formation of those isomers is observed in which the phenolic units connected at the para positions are etherified. This has been established in one case by a single-crystal X-ray analysis. Preliminary results for the extraction of selected alkali and alkaline-earth metals are reported.
Synthesis and Reactivity of 2-Aminophenylpalladium(II) Complexes: Insertion Reactions of Oxygen and Carbon Monoxide into Carbon−Palladium Bonds—New E…
1999
Insertion of CO into 2-aminophenylpalladium complexes leads to 2-aminobenzoylpalladium derivatives. When these compounds are forced to coordinate a carbon donor and a phosphane ligand in the trans position, a C−P coupling process or an insertion of oxygen occurs (see scheme). In this case, a dinuclear palladium complex containing a bridging anthranilato ligand is isolated.
Phosphororganische Verbindungen. 611. Polarographische Untersuchung quartärer Phosphonium- und Arsoniumsalze
1969
Summary The half-wave potentials of a number of quaternary phosphonium and arsonium salts are determined under standard conditions, and their dependence on the concentration of the substrate, the temperature, the drop rate, the height of the mercury head, and the concentration of the capillary-active substance (Triton X-100) is established. It is not possible to deduce from the half-wave potentials which ligands, and in what proportion these ligands, are reductively cleaved. The results suggest that ligands are split off as radicals (transfer, of one electron) and as anions (transfer of two electrons).
ChemInform Abstract: Palladium-Catalyzed Suzuki Carbonylative Reaction of α-Halomethyl Oxime Ethers: A Regioselective Route to Unsymmetrical 1,3-Oxyi…
2015
Über katalytische einflüsse bei der polykondensation des p-kresoldialkohols
1952
Wird natriumfreier p-Kresoldialkohol in Silber- oder Platingeraten bei 130°C kondensiert, so ist durch den Geruch kein Formaldehyd wahrnehmbar. p-Kresoldialkohol enthalt oft von seiner Darstellung uber das Natriumsalz her geringe Mengen an Natrium, dessen Anteil im Bereich von 0,0 bis 5,00/00 liegt (0,000 bis 0,037 Mol Natrium je Mol Phenolalkohol). Die bei der Hartung des p-Kresoldialkohols in Platin- oder Silbergeraten beobachteten Gewichtsverluste und die Formaldehydabspaltung sind umso hoher, je groser der Natriumgehalt ist. Natriumfreier p-Kresoldialkohol in Gefasen aus Jenaer Gerateglas 20 und aus gewohnlichem Glas gehartet zeigt in Ubereinstimmung mit der Abgabefahigkeit an Alkali de…
ChemInform Abstract: Synthesis and Spectroscopic Characterizations of Both 1-Ethyl-4,8- dihydro-10-methoxy-3-methyl-8-R1-6-R2-dipyrazolo(3,4-b:4′,3′-…
2010
The non-selective methylation of compounds 3a-d using ethereal diazomethane, allowed the synthesis of isomers 4 and 5 which were useful intermediates for the preparation, by a simple approach, of the title compounds 7 and 9. A complete assignment of the chemical shifts to the carbon atoms of the compounds 7 and 9 was performed by different nmr experiments, such as DEPT and XHDEPT for onebond CH correlations and COLOC experiments for long-range C-H correlations.