Search results for "Acetylene"

Die dimerisierung von endständigen α-hydroxyacetylenen mit rhodiumkomplexkatalysatoren

1978

Abstract The dimerisation of monosubstituted α-hydroxyacetylenes, which is catalysed by rhodium complexes, yields 1,4-disubstituted vinylacetylenes. The catalyst has been optimized for 3-methylbut-1-yn-3-ol as the substrate by using different ligands. Kinetic measurements were carried out with the monomers 3-methylbut-1-yn-3-ol, 3-methylpent-1-yn-3-ol and 1-ethynylcyclohexan-1-ol. In addition the rates of the dimerisation have been compared with those for a further series of α-hydroxyacetylenes. The by-products from the reaction of 3-methylbut-1-yn-3-ol with [(C 6 H 5 ) 3 P] 3 RhCl as catalyst were determined and the yields of the products compared with those of but-1-yn-3-ol and prop-1-yn-…

1984

1982

Synthesis and Stereochemistry of Diepoxynaphthacenes and Tetraepoxyheptacenes

1997

Cycloaddition reactions of 1,4-dihydro-1,4-epoxynaphthalenes (2) and benzo[c]furans (4), generated in situ from the tetracyclone adducts of 2, yield the diepoxynaphthacenes 5 (Schemes 1, 2). Out of 4 possible stereoisomers an exo-exo and an exo-endo geometry (A and C in Scheme 3) can be realized. The ratio A:C varies from pure A to pure C depending on the substituents of 2 and 4. Stereoisomeric heptacenes 7 can be obtained by a twofold cycloaddition of the same type (Scheme 4). Only one π bond of reactive alkynes such as cyclooctyne or acetylenedicarboxylate is capable of an addition to 4 (Schemes 5, 6).

Quantification of poisons for Ziegler Natta catalysts and effects on the production of polypropylene by gas chromatographic with simultaneous detecti…

2020

[EN] This article describes a new simultaneous method for the analysis of sulfur-type poisons, hydrocarbons and permanent gases affecting the productivity of the Ziegler Natta catalyst during the synthesis of polypropylene on an industrial scale in a fluidized-bed reactor. The identification was achieved employing a configuration of the seven-valve chromatographic system, with events at different times, allowing distribution of the sample through multiple columns, and finally reaching the helium ionization detectors of pulsed discharge, flame ionization and mass spectrometry. The results obtained show a good precision of the method used because the variability was less than 1.02% in area an…

Inhibitory capacities of acetylene on nitrification in two agricultural soils

2000

Abstract Acetylene is currently used to distinguish between the relative contribution of nitrification and denitrification to soil emissions of the greenhouse gas, N 2 O. The basis of this method is that acetylene at low partial pressures inhibits nitrification without affecting N 2 O reduction. This paper reports experiments where low acetylene partial pressures were insufficient to totally inhibit nitrification in an hypercalcareous rendosol at water potentials higher than −3.5 MPa while they were always sufficient in a redoxic luvisol.

Copper(I) Iodide Polyphosphine Adducts at Low Loading for Sonogashira Alkynylation of Demanding Halide Substrates: Ligand Exchange Study between Copp…

2010

The prestabilization of copper iodide with a multidentate ferrocenyl phosphine ligand promotes the palladium-catalyzed cross-coupling of demanding halides with phenylacetylene in a selective way. Novel CuI-triphosphine adducts are described in the solid state and in solution. Their use allowed the introduction of the copper iodide cocatalyst in unprecedented low amounts (0.4 to 0.1 mol %) in systems also employing low amounts of “ligand-free” [PdII(η3-allyl)Cl]2 precursor (0.2 to 0.05 mol %). The scope of substrates is reported, and electronically or sterically deactivated bromides were efficiently coupled. Concerning aryl chlorides, electron-poor activated substrates were also coupled usin…

Atomic absorption spectrometric determination of molybdenum in lubricating oils with use of emulsions

1985

Abstract Samples (0.1 g) containing molybdenum disulphide are digested with aqua regia or with a (1 + 1) hydrofluoric/nitric acid mixture, without complete destruction of the matrix, and the molybdenum is determined in an air/acetylene flame, after emulsification with a non-ionic surfactant (Nemol K-39). The detection limit is ca. 30 μg Mo g−1, and the r.s.d. is 2.9% for 6 analyses of a sample containing 6.5 mg Mo g−1.

Reactions of Alkenes and Alkynes with an Acyclic Silylene and Heavier Tetrylenes under Ambient Conditions

2014

Cycloaddition reactions of the acyclic silylene Si(SAriPr4)2 (AriPr4 = C6H3-2,6(C6H3-2,6-iPr2)2) with a variety of alkenes and alkynes were investigated. Its reactions with the alkynes phenylacetylene and diphenylacetylene and the diene 2,3-dimethyl-1,3-butadiene yielded silacycles (AriPr4S)2tiebar above startSi(CH═tiebar above endCPh) (1), (AriPr4S)2tiebar above startSi(PhC═tiebar above endCPh) (2), and (AriPr4S)2tiebar above startSiCH2CMeCMetiebar above endCH2 (3) at ambient temperature. The compounds were characterized by X-ray crystallography, 1H, 13C, and 29Si NMR spectroscopy, and IR spectroscopy. No reaction was observed with more substituted alkenes such as propene, (Z)-2-butene, te…

A Homoleptic Alkynyl‐Ligated [Au 13 Ag 16 L 24 ] 3− Cluster as a Catalytically Active Eight‐Electron Superatom

2020

A new alkynylated cluster [Au13 Ag16 (C10 H6 NO)24 ]3- is prepared by a NaBH4 mediated reduction method. The AuAg clusters are confirmed by sophisticated characterization techniques. It has a unique "Aucenter @Ag12 @Au12 Ag4 " metal framework which is protected by 24 atypical alkyne ligands L (L=C10 H6 NO). The ligands construct a unique type of motif L-(Ag)-Au-(Ag)-L at the cluster interface, where the alkyne (C≡C) group of each L was linked by sharing an Au atom through the σ bonds and each C≡C group was discretely connected to a chemically different Ag atom (Agicosahedral /Agcap ) through π bonds. The electronic and optical properties of [Au13 Ag16 L24 ]3- were studied. DFT characterized…