Baasandorj Munkhbayar, Stevens Philip S
Institute for Research in Environmental Science, School of Public and Environmental Affairs, and Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
J Phys Chem A. 2007 Feb 1;111(4):640-9. doi: 10.1021/jp066286x.
The rate constants for the reactions of OH and OD with 2-methyl-3-buten-2-ol (MBO) have been measured at 2, 3, and 5 Torr total pressure over the temperature range 300-415 K using a discharge-flow system coupled with laser induced fluorescence detection of OH. The measured rate constants at room temperature and 5 Torr for the OH + MBO reaction in the presence of O2 and the OD + MBO reaction are (6.32 +/- 0.27) and (6.61 +/- 0.66) x 10(-11) cm3 molecule(-1) s(-1), respectively, in agreement with previous measurements at higher pressures. However, the rate constants begin to show a pressure dependence at temperatures above 335 K. An Arrhenius expression of k0 = (2.5 +/- 7.4) x 10(-32) exp[(4150 +/- 1150)/T] cm6 molecule(-2) s(-1) was obtained for the low-pressure-limiting rate constant for the OH + MBO reaction in the presence of oxygen. Theoretical calculations of the energetics of the OH + MBO reaction suggest that the stability of the different HO-MBO adducts are similar, with predicted stabilization energies between 27.0 and 33.4 kcal mol(-1) relative to the reactants, with OH addition to the internal carbon predicted to be 1-4 kcal mol(-1) more stable than addition to the terminal carbon. These stabilization energies result in estimated termolecular rate constants for the OH + MBO reaction using simplified calculations based on RRKM theory that are in reasonable agreement with the experimental values.
利用与激光诱导荧光检测OH相结合的放电流动系统，在2、3和5托的总压力下，于300 - 415K的温度范围内测量了OH和OD与2 - 甲基 - 3 - 丁烯 - 2 - 醇（MBO）反应的速率常数。在室温及5托压力下，O₂存在时OH + MBO反应以及OD + MBO反应的测量速率常数分别为(6.32 ± 0.27)和(6.61 ± 0.66)×10⁻¹¹ cm³分子⁻¹ s⁻¹，这与先前在较高压力下的测量结果一致。然而，在温度高于335K时，速率常数开始呈现出压力依赖性。对于O₂存在时OH + MBO反应的低压极限速率常数，得到了阿仑尼乌斯表达式k₀ = (2.5 ± 7.4)×10⁻³² exp[(4150 ± 1150)/T] cm⁶分子⁻² s⁻¹。OH + MBO反应能量学的理论计算表明，不同HO - MBO加合物的稳定性相似，相对于反应物，预测的稳定化能在27.0至33.4 kcal mol⁻¹之间，OH加成到内部碳上预计比加成到末端碳上稳定1 - 4 kcal mol⁻¹。这些稳定化能通过基于RRKM理论的简化计算得出了OH + MBO反应的估计三分子速率常数，与实验值合理相符。
