title: 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 C(4)H(8) 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 (H(2)C horizontal lineCH) were generated by laser photolysis of vinyl iodide (C(2)H(3)I) 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(1)), 2-butene (k(2)), and isobutene (k(3)) yield k(1) = (1.3 +/- 0.3) x 10(-12) cm(3) molecules(-1) s(-1) exp[-(2200 +/- 120) K/T]; k(2) = (1.7 +/- 0.3) x 10(-12) cm(3) molecules(-1) s(-1) exp[-(2610 +/- 120) K/T]; and k(3) = (1.0 +/- 0.1) x 10(-12) cm(3) molecules(-1) s(-1) exp[-(2130 +/- 50) K/T], respectively. C(6)H(11) 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.
authors.affiliation: Departments of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: C Franklin
authors.initials: CF
authors.lastname: Goldsmith
authors.forename: Huzeifa
authors.initials: H
authors.lastname: Ismail
authors.forename: William H
authors.initials: WH
authors.lastname: Green
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D011312:Pressure; D013696:Temperature; D014753:Vinyl Compounds / Q000737:chemistry*
chemical_list: D000475:Alkenes; D005609:Free Radicals; D014753:Vinyl Compounds; C058602:1-butene; C008176:isobutylene; C021639:2-butene