Pressure and Temperature Dependence of the Reaction of Vinyl Radical with Alkenes III: Measured Rates and Predicted Product Distributions for Vinyl + Butene

Abstract

This work reports experimental and theoretical first-order rate constants for the reaction of vinyl radical with C4H8 alkenes: 1-butene, 2-butene, and iso-butene. The experiments are performed over a temperature range of 300 K to 700 K at 100 Torr. Vinyl radicals (H[subscript 2]C=CH) were generated by laser photolysis of vinyl iodide (C[subscript 2]H[subscript ]3I) at 266 nm, and time-resolved absorption spectroscopy was used to probe vinyl radicals at 423.2 and 475 nm. Weighted Arrhenius fits to the experimental rate coefficients for 1-butene (k[subscript 1]), 2-butene (k[subscript 2]), and iso-butene (k[subscript 3]) yield k[subscript 1] = (1.3±0.3)× 10[superscript -12] cm[superscript 3] molecules[superscript -1] s[superscript -1] exp[-(2200 ± 120) K/T]; k2 = (1.7±0.3)× 10[superscript -12] cm[superscript 3] molecules[superscript -1] s[superscript -1] exp[-(2610 ± 120) K/T]; k[superscript 3] = (1.0±0.1)× 10[superscript -12] cm[superscript 3] molecules[superscript -1] s[superscript -1] exp[-(2130 ± 50) K/T], respectively. C6H11 potential energy surfaces (PES) for each system were calculated using the G3 method. RRKM/ME simulations were performed for each system to predict pressure dependent rate coefficients and branching fractions for the major channels. A generic rate rule for vinyl addition to various alkenes is recommended; a similar rate rule for the abstraction of H atoms by vinyl from alkenes is also provided. Some of the vinyl addition reactions exhibit anomalous Evans-Polanyi plots, similar to those reported for previous methyl addition reactions.