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Gas‐Phase Kinetics of the Thermal 1‐Alkoxy‐1‐vinylcyclopropane to 1‐Alkoxy‐1‐cyclopentene Rearrangement
Author(s) -
McGaffin Gregory,
Meijere Armin De,
Walsh Robin
Publication year - 1991
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19911240439
Subject(s) - chemistry , alkoxy group , ether , arrhenius equation , cyclopentene , alkyl , medicinal chemistry , vinyl ether , diradical , photochemistry , organic chemistry , activation energy , catalysis , polymer , physics , nuclear physics , singlet state , copolymer , excited state
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.