Rate Coefficients and Mechanistic Analysis for Reaction of OH with Vinyl Chloride between 293 and 730 K
journal contributionposted on 21.09.2001, 00:00 by Takahiro Yamada, Masud Siraj, Philip H. Taylor, Jingping Peng, Xiaohua Hu, Paul Marshall
The kinetics of the title reaction were investigated between 293 and 730 K at 740 ± 10 Torr in a helium bath gas. Absolute rate measurements were obtained using a laser photolysis/laser-induced fluorescence (LP/LIF) technique under slow flow conditions. Rate coefficients exhibited complex behavior with negative temperature dependence at temperatures below 560 K, a rapid drop in rate between 560 and 620 K, and a positive temperature dependence above 620 K. The simple Arrhenius equation adequately describes the data at and below 560 K and is given by (in units of cm3 molecule-1 s-1) k(293−560 K) = (2.72 ± 0.35) × 10-12 exp(335 ± 42)/T. Error limits are 2σ values. The low-temperature values for k are within ±2σ of the most recent measurements of this reaction obtained under atmospheric pressure conditions. Above 620 K, our measurement combined with the recent measurements of Liu et al. to yield the following rate expression: k(620−1173 K) = (6.3 ± 4.0) × 10-11 exp(−2740 ± 490)/T. Error limits are 2σ values. The rate data were interpreted using variational transition state theory and QRRK theory. OH addition to the β site followed by adduct stabilization describes the low-temperature measurements. Ab initio-based transition state calculations for the H abstraction channel indicated that this mechanism is consistent with the rate measurements above 620 K. H abstraction is predicted to be the dominant reaction channel above temperatures of 800 K.