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  • 1
    Electronic Resource
    Electronic Resource
    Thermal Rearrangements, XIX. The Kinetics of the Thermal Isomerization of 1-Ethynyl-2,2,3,3-tetramethylcyclopropane (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 377-382 
    Details
    ISSN: 0009-2940
    Keywords: Cyclopropane, 1-ethynyl-2,2,3,3-tetramethyl- ; Isomerization, thermal ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermische Umlagerungen, XIX. - Kinetik der thermischen Isomerisierung von 1-Ethinyl-2,2,3,3-tetramethylcyclopropanDie Darstellung und Gasphasenpyrolyse von 1-Ethinyl-2,2,3,3-tetramethylcyclopropan (9) werden beschrieben. Oberhalb 200°C lagert sich der Kohlenwasserstoff in 4,4,5-Trimethyl-1,2,5-hexatrien (10) und 5,6-Dimethyl-5-hepten-1-in (11) um. Während sich das Allen durch eine 1,5-Wasserstoffwanderung direkt aus 9 bildet, handelt es sich bei dem Alkin um ein Sekundärprodukt, das aus 10 durch eine [3,3]-sigmatrope Umlagerung entsteht. Die Aktivierungsparameter (Ea, lg A) dieser beiden Prozesse wurden im Temperaturbereich von 210-250°C ermittelt. Die erhaltenen Zahlenwerte werden diskutiert und mit denjenigen anderer konzertierter Reaktionen von Alkinen und Alkenen verglichen.
    Notes: 1-Ethynyl-2,2,3,3-tetramethylcyclopropane (9) has been prepared and subjected to gas phase pyrolysis. Above 200°C the hydrocarbon rearranges to 4,4,5-trimethyl-1,2,5-hexatriene (10) and 5,6-dimethyl-5-hepten-1-yne (11). Whereas the allene is produced directly from 9 by a 1,5-hydrogen shift, the alkyne is a secondary product formed from 10 by a [3,3] sigmatropic rearrangement. The activation parameters (Ea, lg A) for both processes have been determined for the 210 to 250°C temperature range. The data are discussed and compared with those for other concerted reactions of alkynes and alkenes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19891220228
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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
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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