Kinetic study of the cyclohexadienyl radical. Part 4.—Combination and disproportionation with the allyl radical

Abstract

The kinetics of the unsensitized thermal decomposition of the allyl ester of cyclohexa-1,4-diene 3-carboxylic acid have been studied in the gas phase between 130 and 200°. The primary dissociation yields equal numbers of allyl and cyclohexadienyl radicals: C₆H₇COOC₃H₅→ C₆H₇·+ CO₂+ C₃H₅·; k₁= 10^{15 ± 2} exp (–40 ± 4)10³/RT sec^–1. The Arrhenius parameters are consistent with significant extension of both dissociating bonds in the activated complex. Interaction between the allyl and cyclohexadienyl radicals conforms to the pattern: [graphic omitted] These results are discussed in relation to the patterns of interaction of the cyclohexadienyl radical with other radical species. Metathesis between the allyl radical and the allyl ester proceeds with an activation energy of 9 kcal/mole.