Search results for "element"

ChemInform Abstract: Trienediolates of Hexadienoic Acids in Synthesis. Synthesis of Retinoic and nor-Retinoic Acids.

2010

Abstract Double deprotonation of either (E,E)-3-methyl-2,4-hexadienoic acid 2, or 4,6-dimethyldihydro-2-pyrone 3 generates apparently the same lithium trienediolate, which affords ω-hydroxy acids 9 on reaction with ketones 7. Hydroxy acids 9 are easily dehydrated to octatrienoic acids 5, which are structurally related to retinoic acid. Similarly, sorbic acid 1 leads to nor-retinoic acid analogs 6.

ChemInform Abstract: Highly Enantioselective Copper(I)-Catalyzed Conjugate Addition of 1,3-Diynes to α,β-Unsaturated Trifluoromethyl Ketones.

2015

The conjugate diynylation of α,β-saturated trifluoromethyl ketones is carried out at low catalytic loading (2.5 mol% for aryl substituents) of a copper(I)—MeO-BIPHEP complex, triethylamine and a terminal 1,3-diyne.

Der Verteilungsraum von physikalisch gelöstem Sauerstoff in wäßrigen Lösungen organischer Substanzen / The Distribution Space of Physically Dissolved…

1976

Abstract In order to evaluate the distribution of molecular oxygen in biological systems, the oxygen solubility (ml/ml atm) at 37 °C in aqueous solutions of thirty organic substances with different concentrations was measured by the classical Van Slyke principle. The oxygen solubility always (with the exception of hemoglobin) decreases exponentially with increasing concentration of the respective substance. In all cases this behavior is described highly significant by a simple empiric exponential function, when the substance concentration as well as the oxygen solubility of pure water is given. The influence of one substance on oxygen solubility contributes additively to the over-all solubi…

Diphosphines of dppf-Type Incorporating Electron-Withdrawing Furyl Moieties Substantially Improve the Palladium-Catalysed Amination of Allyl Acetates

2005

Highly active Pd/diphosphine catalytic systems incorporating new, air-stable ferrocenyl-furylphosphines allow nucleophilic allylic amination at room temperature with unprecedented turnover frequencies. For instance, in the presence of 0.01 mol % catalyst the coupling of aniline to allyl acetate occurs at a TOF of more than 10,000 h - 1 ; even the addition of the less nucleophile morpholine to allyl acetate is observed with a TOF of 4250 h - 1 . The amination of the sterically demanding geranyl acetate, a monoterpene derivative of interest in the flavour industry, at low catalyst loadings demonstrates the scope of this methodology, which provides in addition noticeable advantages in terms of…

ChemInform Abstract: Differential Reactivity of Fluorinated Homopropargylic Amino Esters vs Gold(I) Salts. The Role of the Nitrogen Protecting Group.

2015

The gold(I)-catalyzed hydroarylation/isomerization reaction of N-protected homopropargyl amino esters (III) gives quinoline derivatives of type (IV).

2009

Abstract. Understanding the importance of the different oxidation pathways of sulfur dioxide (SO2) to sulfate is crucial for an interpretation of the climate effects of sulfate aerosols. Sulfur isotope analysis of atmospheric aerosol is a well established tool for identifying sources of sulfur in the atmosphere and assessment of anthropogenic influence. The power of this tool is enhanced by a new ion microprobe technique that permits isotope analysis of individual aerosol particles as small as 0.5 μm diameter. With this new single particle technique, different types of primary and secondary sulfates are first identified based on their chemical composition, and then their individual isotopic…

1976

A radical mechanism is proposed for the formation of the 1,2-polymer 2 in the “spontaneous” polymerization of 4-vinylpyridinium salts 4-VP.HX (X=NO3, ClO4, HSO4, I) in aqueous solution on the basis of strong inhibition by oxygen and other radical inhibitors. Quantitative investigation of the influence of oxygen on the formation of the 1,2-polymer allowed the derivation of a formal kinetic scheme for the initiation and polymerization steps which is consistent with a free radical mechanism. Dependence of the average molecular weight of 2 on monomer concentration is in agreement with this model. Dependence of the inhibition time on the oxygen concentration as well as an acceleration of the fin…

Evidence for the formation of sodium hassate(VIII)

2004

SummaryHassium, element 108, was produced in the fusion reaction between26Mg and248Cm. The hassium recoils were oxidizedin-situto a highly volatile oxide, presumably HsO4, and were transported in a mixture of He and O2to a deposition and detection system. The latter consisted of 16 silicon PIN-photodiodes facing a layer of NaOH, which served, in the presence of a certain partial pressure of water in the transport gas, as reactive surface for the deposition of the volatile tetroxides. Six correlated α-decay chains of Hs were detected in the first 5 detectors centred around detection position 3. In analogy to OsO4, which forms Na2[OsO4(OH)2], an osmate(VIII), with aqueous NaOH, HsO4presumably…

The orientational glass state of argon:Nitrogen and cyanide mixed crystals

1990

Abstract Solid solutions of Ar:N 2 and ( KBr ) 1− x ( KCN ) x mixed crystals show a so-called orientational glass state where the orientations of the aspherical species, N 2 respectively CN - , are frozen in random patterns. The main experimental characteristics of this state and the pertinent theoretical concepts are discussed.

TRIARYL-ARSINE, -STIBENE UND -BISMUTHINE MIT -OR, -NR2-UND -CHR-NMe2-GRUPPEN IN ORTHO-STELLUNG

1983

Abstract Ortho-lithiated alkyl-arylethers, N,N-dialkylarylamines and substituted N,N-dimethylbenzylamines prepared according reaction (1) are reacted with the halides of arsine, antimony and bismuth forming the expected triarylarsines, triarylstibines and triarylbismuthines. By double lithiation the bis-arsine 37 is obtained. Nach (1) hergestellte ortho-lithiierte Alkyl-arylether, N,N-Dialkylarylamine und substituierte N,N-Dimethylbenzylamine werden nach (3) mit Arsen, -Antimon-und Wismutchloriden in die entsprechenden Triarylarsine, Triarylstibine und Triarylbismuthine uberfuhrt. Nach Zweifachlithiierung ist das Bis-arsin 37 zuganglich.