Taylor Sally E, Goddard Andrew, Blitz Mark A, Cleary Patricia A, Heard Dwayne E
School of Chemistry, University of Leeds, Leeds, UK LS2 9JT.
Phys Chem Chem Phys. 2008 Jan 21;10(3):422-37. doi: 10.1039/b711411g. Epub 2007 Nov 7.
The kinetics of reactions of the OH radical with ethene, ethyne (acetylene), propyne (methyl acetylene) and t-butyl-hydroperoxide were studied at temperatures of 69 and 86 K using laser flash-photolysis combined with laser-induced fluorescence spectroscopy. A new pulsed Laval nozzle apparatus is used to provide the low-temperature thermalised environment at a single density of approximately 4x10(16) molecule cm(-3) in N2. The density and temperature within the flow are determined using measurements of impact pressure and rotational populations from laser-induced fluorescence spectroscopy of NO and OH. For ethene, rate coefficients were determined to be k2=(3.22+/-0.46)x10(-11) and (2.12+/-0.12)x10(-11) cm3 molecule(-1) s(-1) at T=69 and 86 K, respectively, in good agreement with a master-equation calculation utilising an ab initio surface recently calculated for this reaction by Cleary et al. (P. A. Cleary, M. T. Baeza Romero, M. A. Blitz, D. E. Heard, M. J. Pilling, P. W. Seakins and L. Wang, Phys. Chem. Chem. Phys., 2006, 8, 5633-5642) For ethyne, no previous data exist below 210 K and a single measurement at 69 K was only able to provide an approximate upper limit for the rate coefficient of k3<1x10(-12) cm3 molecule(-1) s(-1), consistent with the presence of a small activation barrier of approximately 5 kJ mol(-1) between the reagents and the OH-C2H2 adduct. For propyne, there are no previous measurements below 253 K, and rate coefficients of k4=(5.08+/-0.65), (5.02+/-1.11) and (3.11+/-0.09)x10(-12) cm3 molecule(-1) s(-1) were obtained at T=69, 86 and 299 K, indicating a much weaker temperature dependence than for ethene. The rate coefficient k1=(7.8+/-2.5)x10(-11) cm3 molecule(-1) s(-1) was obtained for the reaction of OH with t-butyl-hydroperoxide at T=86 K. Studies of the reaction of OH with benzene and toluene yielded complex kinetic profiles of OH which did not allow the extraction of rate coefficients. Uncertainties are quoted at the 95% confidence limit and include systematic errors.
利用激光闪光光解结合激光诱导荧光光谱技术，在69K和86K的温度下研究了OH自由基与乙烯、乙炔、丙炔（甲基乙炔）和叔丁基过氧化氢的反应动力学。使用一种新型脉冲拉瓦尔喷嘴装置在氮气中提供单一密度约为4×10¹⁶分子·厘米⁻³的低温热平衡环境。通过测量NO和OH的激光诱导荧光光谱中的冲击压力和转动布居来确定气流中的密度和温度。对于乙烯，在T = 69K和86K时，速率系数分别确定为k₂ = (3.22 ± 0.46)×10⁻¹¹和(2.12 ± 0.12)×10⁻¹¹厘米³·分子⁻¹·秒⁻¹，这与利用Cleary等人（P. A. Cleary、M. T. Baeza Romero、M. A. Blitz、D. E. Heard、M. J. Pilling、P. W. Seakins和L. Wang，《物理化学化学物理》，2006年，8，5633 - 5642）最近为该反应计算的从头算表面进行的主方程计算结果高度一致。对于乙炔，在210K以下没有先前的数据，在69K的单次测量仅能给出速率系数k₃ < 1×10⁻¹²厘米³·分子⁻¹·秒⁻¹的近似上限，这与反应物和OH - C₂H₂加合物之间存在约5 kJ·mol⁻¹的小活化能垒一致。对于丙炔，在253K以下没有先前的测量数据，在T = 69K、86K和299K时获得的速率系数分别为k₄ = (5.08 ± 0.65)、(5.02 ± 1.11)和(3.11 ± 0.09)×10⁻¹²厘米³·分子⁻¹·秒⁻¹，表明其温度依赖性比乙烯弱得多。在T = 86K时，OH与叔丁基过氧化氢反应的速率系数k₁ = (7.8 ± 2.5)×10⁻¹¹厘米³·分子⁻¹·秒⁻¹。对OH与苯和甲苯反应的研究得到了OH复杂的动力学曲线，无法提取速率系数。不确定度以95%置信限给出，包括系统误差。
