Blázquez Sergio, González Daniel, García-Sáez Alberto, Antiñolo María, Bergeat Astrid, Caralp Françoise, Mereau Raphaël, Canosa André, Ballesteros Bernabé, Albaladejo José, Jiménez Elena
Departamento de Química Física. Facultad de Ciencias y Tecnologías Químicas. Universidad de Castilla-La Mancha, Avda. Camilo José Cela, 1B. 13071 Ciudad Real, Spain.
Instituto de Investigación en Combustión y Contaminación Atmosférica (ICCA). Universidad de Castilla-La Mancha, Camino de Moledores s/n. 13071 Ciudad Real, Spain.
ACS Earth Space Chem. 2019 Sep 19;3(9):1873-1883. doi: 10.1021/acsearthspacechem.9b00144. Epub 2019 Aug 12.
The rate coefficient, (), for the gas-phase reaction between OH radicals and acetone CHC(O)CH, has been measured using the pulsed CRESU (French acronym for Reaction Kinetics in a Uniform Supersonic Flow) technique ( = 11.7-64.4 K). The temperature dependence of ( = 10-300 K) has also been computed using a RRKM-Master equation analysis after partial revision of the potential energy surface. In agreement with previous studies we found that the reaction proceeds via initial formation of two pre-reactive complexes both leading to HO + CHC(O)CH by H-abstraction tunneling. The experimental () was found to increase as temperature was lowered. The measured values have been found to be several orders of magnitude higher than (300 K). This trend is reproduced by calculations, with a special good agreement with experiments below 25 K. The effect of total gas density on () has been explored. Experimentally, no pressure dependence of (20 K) and (64 K) was observed, while (50 K) at the largest gas density 4.47×10 cm is twice higher than the average values found at lower densities. The computed () is also reported for 10 cm of He (representative of the interstellar medium). The predicted rate coefficients at 10 K surround the experimental value which appears to be very close to the low pressure regime prevailing in the interstellar medium. For gas-phase model chemistry of interstellar molecular clouds, we suggest using the calculated value of 1.8×10 cm molecule s at 10 K and the reaction products are water and CHC(O)CH radicals.
采用脉冲CRESU（均匀超音速流中反应动力学的法语首字母缩写）技术（温度范围为11.7 - 64.4 K）测量了OH自由基与丙酮CH₃C(O)CH₃之间气相反应的速率系数(k)。在对势能面进行部分修正后，还使用RRKM - 主方程分析计算了k在10 - 300 K范围内随温度的变化关系。与先前的研究一致，我们发现该反应通过最初形成两个预反应复合物进行，二者均通过氢提取隧穿生成HO + CH₃C(O)CH₂。实验发现k随温度降低而增大。测量值比k(300 K)高几个数量级。计算结果重现了这一趋势，在低于25 K时与实验结果吻合得特别好。研究了总气体密度对k的影响。实验上，未观察到k(20 K)和k(64 K)与压力有关，而在最大气体密度4.47×10¹⁹ cm⁻³时k(50 K)是在较低密度下发现的平均值的两倍。还报告了10¹⁰ cm⁻³的He（代表星际介质）条件下计算得到的k。在10 K时预测的速率系数围绕着实验值，该实验值似乎非常接近星际介质中普遍存在的低压状态。对于星际分子云的气相模型化学，我们建议使用在10 K时计算得到的1.8×10⁻¹⁰ cm³ molecule⁻¹ s⁻¹的值，反应产物是水和CH₃C(O)CH₂自由基。
