Kinetics of the thermal gas phase reactions of methylspiro[2,2]pentane

In the temperature range 317·5–391·3 °C methylspiro[2,2]pentane decomposes via five competing homogeneous unimolecular pathways yielding ethylidenecyclobutane (k1), 2-methyl(methylene)cyclobutane (k2), 3-methyl-(methylene)cyclobutane (k3), ethylene + buta-1,2-diene (k4), and allene + propene (k5). 3-Methyl(methylene)-k1/s–1= 1014·14 ∓ 0·15 exp [–(53 816 ∓ 415)/1·987T], k2/s–1= 1014·52 ∓ 0·14 exp [–(53,817 ∓ 412)/1·987T], k3/s–1= 1014·38 ∓ 0·15 exp [–(53,817 ∓ 416)/1·987T], k4/s–1= 1015·48 ∓ 0·42 exp [–(59,616 ∓ 1208)/1·987T], k5/s–1= 1015·32 ∓ 0·59 exp [–(59,795 ∓ 1672)/1·987T], k12/s–1= 1014·16 ∓ 1·15 exp [–(52,910 ∓ 3300)/1·987T] cyclobutane in the same temperature range isomerizes homogeneously to 2-methylpenta-1,4-diene (k12). The mechanisms of the various reactions are discussed in terms of the formation of diradical intermediates.