Vimal Deepali, 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. 2006 Oct 12;110(40):11509-16. doi: 10.1021/jp063224y.
The kinetics of the reactions of OH with acetic acid, acetic acid-d3 and acetic acid-d4 were studied from 2 to 5 Torr and 263-373 K using a discharge flow system with resonance fluorescence detection of the OH radical. The measured rate constants at 300 K for the reaction of OH with acetic acid and acetic acid-d4 (CD3C(O)OD) were (7.42+/-0.12)x10(-13) and (1.09+/-0.18)x10(-13) cm3 molecule-1 s-1 respectively, and the rate constant for the reaction of OH with acetic acid-d3 (CD3C(O)OH) was (7.79+/-0.16)x10(-13) cm3 molecule-1 s-1. These results suggest that the primary mechanism for this reaction involves abstraction of the acidic hydrogen. Theoretical calculations of the kinetic isotope effect as a function of temperature are in good agreement with the experimental measurements using a mechanism involving the abstraction of the acidic hydrogen through a hydrogen-bonded complex. The rate constants for the OH+acetic acid and OH+acetic acid-d4 reactions display a negative temperature dependence described by the Arrhenius equations kH(T)=(2.52+/-1.22)x10(-14) exp((1010+/-150)/T) and kD(T)=(4.62+/-1.33)x10(-16) exp((1640+/-160)/T) cm3 molecule-1 s-1 for acetic acid and acetic acid-d4, respectively, consistent with recent measurements that suggest that the lifetime of acetic acid at the low temperatures of the upper troposphere is shorter than previously believed.
在2至5托以及263 - 373 K的条件下，使用带有OH自由基共振荧光检测的放电流动系统，研究了OH与乙酸、乙酸 - d3和乙酸 - d4的反应动力学。在300 K时，测得OH与乙酸和乙酸 - d4（CD3C(O)OD）反应的速率常数分别为(7.42±0.12)×10⁻¹³和(1.09±0.18)×10⁻¹³ cm³·分子⁻¹·秒⁻¹，OH与乙酸 - d3（CD3C(O)OH）反应的速率常数为(7.79±0.16)×10⁻¹³ cm³·分子⁻¹·秒⁻¹。这些结果表明，该反应的主要机制涉及酸性氢的提取。作为温度函数的动力学同位素效应的理论计算结果与使用涉及通过氢键复合物提取酸性氢的机制的实验测量结果高度吻合。OH + 乙酸和OH + 乙酸 - d4反应的速率常数呈现负温度依赖性，乙酸和乙酸 - d4的阿伦尼乌斯方程分别为kH(T)=(2.52±1.22)×10⁻¹⁴ exp((1010±150)/T)和kD(T)=(4.62±1.33)×10⁻¹⁶ exp((1640±160)/T) cm³·分子⁻¹·秒⁻¹，这与最近的测量结果一致，表明对流层上部低温下乙酸的寿命比之前认为的要短。
