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  • 1985-1989
  • 1980-1984  (3)
  • 1960-1964  (3)
  • 1950-1954
  • 1870-1879
  • 1982  (3)
  • 1964  (3)
  • 1950
  • Catalysis
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 18 (1982), S. 351-353 
    ISSN: 1432-1432
    Keywords: HCN ; HCN Oligomers ; Chemical Evolution ; Primitive Earth ; Formaldehyde ; Cyanohydrins ; Catalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Formaldehyde and other simple carbonyl compounds are known to react rapidly with HCN in aqueous solution to produce the corresponding cyanohydrin compounds. We have observed that these cyanohydrins markedly accelerate the rate of HCN oligomeri-zation, both in homogeneous solution as well as in the frozen state. These results, for which a tentative mechanism is suggested, significantly extend the possible range of conditions for HCN oligomerization on the prebiotic Earth.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 21 (1982), S. 117-130 
    ISSN: 0570-0833
    Keywords: Fischer-Tropsch synthesis ; Catalysis ; Cluster compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Fischer-Tropsch Synthesis counts among the industrial-scale processes having a versatile and broad product range, and has for decades offered the most attractive possibility for the use of coal as a source of heating oil and fuels. This conceivably simple reaction, the catalytic hydrogenation of carbon monoxide, generally leads to simple hydrocarbons as well (i.e. short chain olefins) that have been sought as chemical feedstocks since the oil crisis of the seventies, but fails to provide the large-scale, economic process required, due in large part to the minimal selectivity of traditional Fischer-Tropsch processes. In an effort to solve this problem current research in this sector is concerned not only with the optimization of old and the development of new catalytic systems, but also increasingly with the elucidation of numerous relevant reaction mechanisms. This article will discuss, from the viewpoint of an organometallic chemist, the significance of typical model reactions, both with regard to some fundamental aspects of synthesis gas chemistry, and in comparison with previous views concerning the mechanism of the Fischer-Tropsch Synthesis. The importance of various unique classes of complexes that have been studied in the context of Fischer-Tropsch chemistry is also evaluated with regard to their importance in the synthesis of hydrocarbons from carbon monoxide and hydrogen. It emerges that the primary steps of the reductive oligomerization of carbon monoxide are best described by the carbide/methylene mechanism, as originally proposed by Hans Fischer and Franz Tropsch.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0570-0833
    Keywords: Electron transfer catalysis ; Electrocatalysis ; Reaction mechanisms ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The concept of electron transfer catalysis (ETC), or more specifically “Double Activation Induced by Single Electron Transfer” (DAISET) gives an opportunity to connect experimental facts never previously correlated. The first activation results from the transfer of an electron to (or from) a molecular species; the second activation results from the build-up of a reaction chain able to reproduce the species formed in the first step. The starting point of this review is the SRN1 mechanism where principle and experimental diagnostic criteria are critically discussed. The thermal and photochemical exchange and substitution reactions of PtIV complexes are then reviewed together with the exchange reaction [AuCl4]-/Cl-, reactions with Grignard reagents and other organometallic reagents, as well as the redox behavior of electronically excited organic compounds. Photochemical applications, including solar energy conversion are discussed. New aspects are also presented for the mechanistic problem “SN2 reaction or SET process?” Moreover, the concept has significance for SH2 reactions at metal centers, molecule-induced homolyses, reactions of complexes, as well as electrochemical processes.-Unless otherwise specified, only double activation (DAISET) processes will be discussed in this article.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0570-0833
    Keywords: Proton transfer ; Catalysis ; Enzyme catalysis ; Hydrolysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 93-101 
    ISSN: 0570-0833
    Keywords: Organometallic catalysts ; Catalysis ; Reaction mechanisms ; Lithium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 3 (1964), S. 185-191 
    ISSN: 0570-0833
    Keywords: Coordination modes ; Catalysis ; Cyclooctatetraenes ; Reppe chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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