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

摘要

This work reports experimental and theoretical first-order rate constants for the reaction of vinyl radical with C4H8 alkenes: 1-butene, 2-butene, and isobutene. The experiments are performed over a temperature range of 300 to 700 K at 100 Torr. Vinyl radicals (H2CdCH) were generated by laser photolysis of vinyl iodide (C2H3I) 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 (k1), 2-butene (k2), and isobutene (k3) yield k1 ) (1.3 ( 0.3) × 10-12 cm3 molecules-1 s-1 exp[-(2200 ( 120) K/T]; k2 ) (1.7 ( 0.3) × 10-12 cm3 molecules-1 s-1 exp[-(2610 ( 120) K/T]; and k3 ) (1.0 ( 0.1) × 10-12 cm3 molecules-1 s-1 exp[-(2130 ( 50) K/T], respectively. C6H11 potential energy surfaces (PESs) 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.