Kinetics of the thermal gas-phase reactions of ethylidenecyclobutane

Abstract

In the temperature range 310–424 °C ethylidenecyclobutane undergoes a reversible homogeneous unimolecular isomerisation to 2-methylmethylenecyclobutane; k₁/s^–1= 10^{13·92 ± 0·36} exp [–(49,280 ± 1000)/1·987T]; k_–1/s^–1= 10^{13·68 ± 0·36} exp [–(48,890 ± 1000)/1·987T]. Much slower competing reactions also occur giving 2-ethylbuta-1,3-diene {k/s^–1= 10^{13·08 ± 1·64} exp [–(54,650 ± 4780)/1·987T]}, ethylene + buta-1,2-diene {k/s^–1= 10^{15·25 ± 1·33} exp [–(61,680 ± 970)/1·987T]}, and propene + allene {k/s^–1= 10^{14·69 ± 0·93} exp [–(62,630 ± 2850)/1·987T]}. The mechanism for the formation of all products is discussed in terms of a mechanism involving the fission of an allylic bond of the methylenecyclobutane to give a diradical which may then recyclise, or undergo an intramolecular hydrogen transfer, or decompose.