School of Chemistry, University of Leeds , Leeds, LS2 9JT, United Kingdom.
J Phys Chem A. 2013 Oct 17;117(41):10736-45. doi: 10.1021/jp406522z. Epub 2013 Oct 8.
The rate coefficients for the reaction of OH with the alkyl amines: methylamine (MA), dimethylamine (DMA), trimethylamine (TMA), and ethylamine (EA) have been determined using the technique of pulsed laser photolysis with detection of OH by laser-induced fluorescence as a function of temperature from 298 K to ∼600 K. The rate coefficients (10(11) × k/cm(3) molecule(-1) s(-1)) at 298 K in nitrogen bath gas (typically 5-25 Torr) are: k(OH+MA) = 1.97 ± 0.11, k(OH+DMA) = 6.27 ± 0.63, k(OH+TMA) = 5.78 ± 0.48, k(OH+EA) = 2.50 ± 0.13. The reactions all show a negative temperature dependence which can be characterized as: k(OH+MA) = (1.889 ± 0.053) × 10(-11)(T/298 K)(-(0.56±0.10)), k(OH+DMA) = (6.39 ± 0.35) × 10(-11)(T/298 K)(-(0.75±0.18)), k(OH+TMA) = (5.73 ± 0.15) × 10(-11)(T/298 K)(-(0.71±0.10)), and k(OH+EA) = (2.54 ± 0.08) × 10(-11)(T/298 K)(-(0.68±0.10)). OH and OD reactions have very similar kinetics. Potential energy surfaces (PES) for the reactions have been characterized at the MP2/aug-cc-pVTZ level and improved single point energies of stationary points obtained in CCSD(T) and CCSD(T*)-F12a calculations. The PES for all reactions are characterized by the formation of pre- and post-reaction complexes and submerged barriers. The calculated rate coefficients are in good agreement with experiment; the overall rate coefficients are relatively insensitive to variations of the barrier heights within typical chemical accuracy, but the branching ratios vary significantly. The rate coefficients for the reactions of OH/OD with MA, DMA, and EA do not vary with added oxygen, but for TMA a significant reduction in the rate coefficient is observed consistent with OH recycling from a chemically activated peroxy radical. OH regeneration is pressure-dependent and is not significant at 298 K and atmospheric pressure, but the efficiency of recycling increases strongly with temperature. The PES for OH recycling have been calculated. There is evidence that the primary process in TMA photolysis at 248 nm is the loss of H atoms.
OH 与烷基胺反应的速率系数：甲胺（MA）、二甲胺（DMA）、三甲胺（TMA）和乙胺（EA），已使用脉冲激光光解技术在 298 K 至约 600 K 的温度范围内确定，通过激光诱导荧光检测 OH。在氮气浴（通常为 5-25 托）中，298 K 时的速率系数（10(11) × k/cm(3) 分子(-1) s(-1)）为：k(OH+MA) = 1.97 ± 0.11，k(OH+DMA) = 6.27 ± 0.63，k(OH+TMA) = 5.78 ± 0.48，k(OH+EA) = 2.50 ± 0.13。所有反应均表现出负温度依赖性，可表示为：k(OH+MA) = (1.889 ± 0.053) × 10(-11)(T/298 K)(-(0.56±0.10))，k(OH+DMA) = (6.39 ± 0.35) × 10(-11)(T/298 K)(-(0.75±0.18))，k(OH+TMA) = (5.73 ± 0.15) × 10(-11)(T/298 K)(-(0.71±0.10))，k(OH+EA) = (2.54 ± 0.08) × 10(-11)(T/298 K)(-(0.68±0.10))。OH 和 OD 反应具有非常相似的动力学。在 MP2/aug-cc-pVTZ 水平下对反应的势能面（PES）进行了表征，并在 CCSD(T)和 CCSD(T*)-F12a 计算中获得了改进的驻点单点能。所有反应的 PES 均由预反应和后反应复合物以及淹没的势垒特征化。计算出的速率系数与实验吻合良好；总体速率系数对典型化学精度内势垒高度的变化相对不敏感，但分支比变化显著。OH/OD 与 MA、DMA 和 EA 的反应速率系数不受添加氧的影响，但对于 TMA，观察到速率系数显著降低，这与化学活化过氧自由基的 OH 再循环一致。OH 再生与压力有关，在 298 K 和大气压下并不显著，但随着温度的升高，再循环效率会强烈增加。已计算出 OH 再循环的 PES。有证据表明，248 nm 时 TMA 光解的主要过程是失去 H 原子。
