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

Abstract

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= 10^{14·14 ∓ 0·15} exp [–(53 816 ∓ 415)/1·987T], k₂/s^–1= 10^{14·52 ∓ 0·14} exp [–(53,817 ∓ 412)/1·987T], k₃/s^–1= 10^{14·38 ∓ 0·15} exp [–(53,817 ∓ 416)/1·987T], k₄/s^–1= 10^{15·48 ∓ 0·42} exp [–(59,616 ∓ 1208)/1·987T], k₅/s^–1= 10^{15·32 ∓ 0·59} exp [–(59,795 ∓ 1672)/1·987T], k₁₂/s^–1= 10^{14·16 ∓ 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.