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  • 1
    Electronic Resource
    Electronic Resource
    Gas-Phase Kinetics of Pyrolysis of 3,3-Dimethylcyclopropene and Its 1-Trimethylsilyl Derivative The Effect of Silyl Substitution on Cyclopropene Isomerisation (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 637-642 
    Details
    ISSN: 0009-2940
    Keywords: Cyclopropene, 3,3-dimethyl-1-trimethylsilyl- ; Cyclopropene, isomerisation ; Gas-phase kinetics ; Ring-opening of 3,3-dimethylcyclopropene ; Vinylcarbene intermediates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Gas-Phasen-Kinetik der Pyrolyse von 3,3-Dimethylcyclopropen und seinem 1-Trimethylsilyl-Derivat. - Der Effekt der Silyl-Substitution auf die Cyclopropen-IsomerisierungDie Gasphasen-Pyrolyse von 3,3-Dimethylcyclopropen (1) im Temperaturbereich 185-225°C ergibt 3-Methyl-1-butin (2) (91%) und Isopren (3) (9%). Die Gasphasen-Pyrolyse von 3,3-Dimethyl-1-trimethylsilylcyclopropen (4) führt zu 3-Methyl-1-trimethylsilyl-1-butin (5) (99%) und trans-3-Methyl-1-trimethylsilyl-1,3-butadien (6) (1%). Beide Umlagerungen sind homogene, unimolekulare Reaktionen erster Ordnung mit den folgenden druck-unabhängigen Arrhenius-Parametern.Überraschenderweise desaktiviert die Trimethylsilyl-Gruppe das Cyclopropen in bezug auf seine Isomerisierung. Mögliche Mechanismen werden diskutiert.
    Notes: The gas-phase pyrolysis of 3,3-dimethylcyclopropene (1) in the temperature range of 185-225°C gives 3-methyl-1-butyne (2) (91%) and isoprene (3) (9%). The gas-phase pyrolysis of 3,3-dimethyl-1-trimethylsilylcyclopropene (4) in the temperature range of 195-235°C gives 3-methyl-1-trimethylsilyl-1-butyne (5) (99%) and trans-3-methyl-1-trimethylsilyl-1,3-butadiene (6) (1%). Both rearrangements are homogeneous, first-order, unimolecular reactions with the following pressure-independent Arrhenius parameters.Rather surprisingly, the trimethylsilyl group deactivates cyclopropene with respect to its isomerisation. Possible mechanisms are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19891220409
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  • 2
    Electronic Resource
    Electronic Resource
    Gas-Phase Kinetics of the Thermal 1-Alkoxy-1-vinylcyclopropane to 1-Alkoxy-1-cyclopentene Rearrangement (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 939-945 
    Details
    ISSN: 0009-2940
    Keywords: 1-Vinylcyclopropane ; 1-methoxy- ; 1-ethoxy- ; Vinylcyclopropane ; isomerization ; Gas-phase kinetics ; Ring expansion of 1-alkoxy-1-vinylcyclopropanes ; Diradical intermediates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title studies have been carried out with both 1-vinyl-1-cyclopropyl methyl ether (1-OMe) and 1-vinyl-1-cyclopropyl ethyl ether (1-OEt) in the temperature ranges 274.6-324.5 and 273.6 - 323.0°C, respectively. Both reactions predominantly give the vinylcyclopropane-cyclopentene (VCP-CP) rearrangement products 1-cyclopenten-1-yl methyl ether (2-OMe) and 1-cyclopenten-1-yl ethyl ether (2-OEt). Additionally, 2-OEt eliminates ethene (3) in a consecutive reaction at a lower reaction rate compared with the VCP-CP rearrangement. The rearrangements obey first-order kinetics and have been shown to be homogeneous, pressure-independent reactions with the following Arrhenius equations:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {1 - {\rm OMe:}} {{\rm lg}\left({k/s^{-1}} \right) = \left({13.89 \pm 0.23} \right) - \left({191.30 \pm 2.55{\rm kJ mol}^{-1}} \right)/RT\ln 10} \\\end{array} $$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {1 - {\rm OMt:}} {{\rm lg}\left({k/s^{-1}} \right) = \left({13.77 \pm 0.01} \right) - \left({188.80 \pm 1.85{\rm kJ mol}^{-1}} \right)/RT\ln 10} \\\end{array} $$\end{document}The Arrhenius parameters represent reliable values for general 1-vinyl-1-cyclopropyl alkyl ether→1-cyclopenten-1-yl-alkyl ether (1-OR→2-OR) rearrangements within a large temperature interval in the gas phase. The results support a mechanism proceeding via a diradical. The stabilizing effect of methoxy substitution is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240439
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal Rearrangements, XX[1] The Kinetics of Thermal Isomerisation of 4-Methyl-1,2,5-hexatriene in the Gas Phase (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 711-721 
    Details
    ISSN: 0009-2940
    Keywords: 1,2,5-Hexatriene, 4-methyl-, thermal isomerisation ; Kinetic measurements ; Thermal isomerisations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4-Methyl-1,2,5-hexatriene (13) has been prepared and subjected to gas-phase pyrolysis. Above 220°C, 13 rearranges reversibly to both trans-5-hepten-1-yne (14) and its cis-isomer 15. Formation of 14 is faster than that of 15. These isomerisations are accompanied by a slower irreversible rearrangement to 1-methyl-4-methylene-1-cyclopentene (16) and 1-methyl-3-methylene-1-cyclopentene (17). Rate constants and Arrhenius parameters have been obtained for all these reactions which were shown to be homogeneous and unimolecular. For the processes 13 ⇄ 14 and 13 ⇄ 15 the data are consistent with [3,3] Cope-type sigmatropic rearrangements. For the process 13 → 16 + 17, a rate-determining formation of the 1-methyl-3-methylenecyclopentane-2,5-diyl diradical is proposed. The rearrangements form a consistent pattern with other known examples. - The equilibrium data are shown to be in good agreement with thermodynamic estimates based on Group Additivity. The additivity scheme of Benson required extension to provide values for two new group contributions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250326
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