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Thermal Rearrangements, XIX. The Kinetics of the Thermal Isomerization of 1‐Ethynyl‐2,2,3,3‐tetramethylcyclopropane
Author(s) -
Hopf Henning,
Wachholz Gerhard,
Walsh Robin,
de Meijere Armin,
Teichmann Stefan
Publication year - 1989
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.19891220228
Subject(s) - chemistry , isomerization , sigmatropic reaction , allene , alkyne , hydrocarbon , pyrolysis , kinetics , hydrogen , atmospheric temperature range , photochemistry , cope rearrangement , thermal decomposition , medicinal chemistry , organic chemistry , catalysis , thermodynamics , physics , quantum mechanics
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 ( E a , 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.