论文信息 - Gas‐Phase Kinetics of Pyrolysis of 3,3‐Dimethylcyclopropene and Its 1‐Trimethylsilyl Derivative The Effect of Silyl Substitution on Cyclopropene Isomerisation

Gas‐Phase Kinetics of Pyrolysis of 3,3‐Dimethylcyclopropene and Its 1‐Trimethylsilyl Derivative The Effect of Silyl Substitution on Cyclopropene Isomerisation

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. Gas-Phasen-Kinetik der Pyrolyse von 3,3-Dimethylcyclopropen und seinem 1-Trimethylsilyl-Derivat. – Der Effekt der Silyl-Substitution auf die Cyclopropen-Isomerisierung Die 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) fuhrt 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-unabhangigen Arrhenius-Parametern. Uberraschenderweise desaktiviert die Trimethylsilyl-Gruppe das Cyclopropen in bezug auf seine Isomerisierung. Mogliche Mechanismen werden diskutiert.

R. Walsh | A. Meijere | S. Untiedt | M. Stohlmeier

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