The reaction of vinyl radical with alkenes: measured rates and predicted pressure-dependent product distributions.

摘要

This work reports experimental and theoretical determination of first-order rate constants for the reaction of vinyl radical with the five smallest alkenes: ethene, propene, 1-butene, 2-butene, and iso-butene. The experiments were performed over a temperature range of 300 K to 700 K at 100 Torr. Vinyl radicals (H2C=CH) 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. The C4H7, C5H9, and C6H_(11) potential energy surfaces (PES) for each system were calculated using the G3 method in Gaussian 03. RRKM/ME simulations were performed using VariFlex on a simplified PES for each system to predict pressure dependent rate coefficients and branching fractions for the major channels. A weighted Arrhenius fit to the experimental rate constant at 100 Torr for each alkene is presented. 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.