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  • 1960-1964  (6)
  • 1935-1939
  • 1920-1924
  • 1964  (6)
  • Catalysis  (3)
  • Fibers
  • Heterocycles
  • Key words
  • Phosphorus
Materialart
Erscheinungszeitraum
  • 1960-1964  (6)
  • 1935-1939
  • 1920-1924
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 453-460 
    ISSN: 0570-0833
    Schlagwort(e): Tetradentate ligands ; P ligands ; Arsenic ligands ; Phosphorus ; Arsenic ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effect of ligand shape on coordination numbers and geometry of coordination compounds has been studied using two tetradentate ligands containing phosphorus and arsenic. These tend to form five-coordinate complexes with trigonal bipyramidal structure [Fe(II), Co(I), Co(II), Rh(I), Ni(II), Pd(II), Pt(II)], but can also form six-coordinate complexes with octahedral structure [Fe(II), Ru(II), Os(II), Co(III), Rh(III), Pd(IV), Pt(IV)]. The magnetic properties and the stereochemistry of the complexes are explained by ligand field theory which predicts that, for metal ions with d6-electronic configuration, a low overall field strength should favor the formation of five-coordinate paramagnetic complexes while a high overall field strength should favor the formation of six-coordinate diamagnetic complexes. - This work provides further indication that the tendency of polydentate ligands to use all the potential donor atoms is not as pronounced as is generally believed. This is shown by the isolation of chromium(III) complexes in which the tetradentate ligands are, in fact, acting as tridentate, and by the isolation of mercury(II) complexes where only two of the four donor atoms of the polydentate ligand are actually bonded to the central metal atom.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 0570-0833
    Schlagwort(e): Proton transfer ; Catalysis ; Enzyme catalysis ; Hydrolysis ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The proton occupies a special position as a promoter and mediator in chemical reactions occurring in solution. Many reactions in organic chemistry are catalysed by acids or bases; likewise, most enzymes contain active groups which promote acid-base catalysis. To understand the reaction mechanisms involved, it is necessary to identify the elementary steps as well as their course in time. Systematic investigation of these elementary steps as well as their course in time. Systematic investigation of these elementary steps has become possible only with the development of new methods for studying very fast reactions. The present paper reviews the information obtained in this type of investigation. The result is a relatively complete picture of the elementary proton transfer mechanisms and a comprehensive description of the modes and laws of acid-base and enzymatic catalysis.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 93-101 
    ISSN: 0570-0833
    Schlagwort(e): Organometallic catalysts ; Catalysis ; Reaction mechanisms ; Lithium ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Kinetic investigations of the polyreaction of isoprene with organolithium compounds as initiators in n-heptane as solvent indicate the following sequence of reactions: 1. formation of an adduct between a monomeric form of the organolithium compound and the isoprene and 2. reaction of this adduct with an associated form of the organolithium compound with insertion of the isoprene. The adduct formation is considered to be due to chemisorption, and proof of such chemisorption of a monomer (ethylene) is also demonstrated for a homogeneous Ziegler-type catalyst. All the reactions can be formulated in the form of cyclic structures with electron-deficient character. Postulation of such ring structures explains the surprising values obtained for the frequency factors and equilibrium constants.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 185-191 
    ISSN: 0570-0833
    Schlagwort(e): Coordination modes ; Catalysis ; Cyclooctatetraenes ; Reppe chemistry ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The relationship between the structure and the catalytic activity of nickel(II) complexes in the synthesis of cyclooctatetraene by the method of W. Reppe is discussed. The cyclotetramerization of acetylene takes place within labile Ni(II)-acetylene π-complexes. Inhibition tests have made it probable that four molecules of acetylene are grouped around the nickel ion in the transition state, in a configuration which favors the formation of the eight-membered ring.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 333-341 
    ISSN: 0570-0833
    Schlagwort(e): Strained molecules ; Heterocycles ; Diaziridines ; Diazirines ; Oxaziranes ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Since their discovery five years ago, the diaziridines have become an extensive and easily accessible class of compounds. Hydrolysis of these compounds effects a simple synthesis of hydrazine, alkylhydrazines, and N,N′-dialkylhydrazines. They are also powerful oxidizing agents. The rigidity of the three-membered ring gives rise to a few stereoelectronic peculiarities. Investigations on the mechanism of formation of the three-membered rings led to a new synthesis of oxaziranes and to discovery of the isomeric oximes with a three-membered ring structure. The latter decompose readily to form diimide. Diazirines are cyclic isomers of the aliphatic diazo compounds and are surprisingly easy to obtain by dehydrogenation of suitable diaziridines; they are chemically much more stable than the linear isomers. Grignard reagents add onto the N=N double bond without destruction of the three-membered ring. Thermal decomposition yields carbenes.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 460-470 
    ISSN: 0570-0833
    Schlagwort(e): Heat resistance ; Fibers ; Polymers ; Materials science ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This survey is principally concerned with papers published since 1959 on hydrocarbon polymers, aliphatic poly(terephthalamide) fibers, poly(hydroxybenzoic acid) films, poly(oxadiazole) fibers, poly(benzimidazole) films, poly(phenyltriazole) films, poly(pyromellitimide) films, and fibers from cyclized poly(acrylonitrile). All these materials have extremely high melting points and satisfactory in-use characteristics at high temperatures.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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