Eskola Arkke J, Geppert Wolf D, Rissanen Matti P, Timonen Raimo S, Halonen Lauri
Laboratory of Physical Chemistry, P.O. Box 55 (A.I. Virtasen aukio 1), FIN-00014 University of Helsinki, Finland.
J Phys Chem A. 2005 Jun 23;109(24):5376-81. doi: 10.1021/jp050441a.
The kinetics of the reactions of chlorinated methyl radicals (CH2Cl, CHCl2, and CCl3) with NO2 have been studied in direct measurements at temperatures between 220 and 360 K using a tubular flow reactor coupled to a photoionization mass spectrometer. The radicals have been homogeneously generated at 193 or 248 nm by pulsed laser photolysis of appropriate precursors. Decays of radical concentrations have been monitored in time-resolved measurements to obtain the reaction rate coefficients under pseudo-first-order conditions with the amount of NO2 being in large excess over radical concentrations. The bimolecular rate coefficients of all three reactions are independent of the bath gas (He or N2) and pressure within the experimental range (1-6 Torr) and are found to depend on temperature as follows: k(CH2Cl + NO2) = (2.16 +/- 0.08) x 10(-11) (T/300 K)(-1.12+/-0.24) cm3 molecule(-1) s(-1) (220-363 K), k(CHCl2 + NO2) = (8.90 +/- 0.16) x 10(-12) (T/300 K)(-1.48+/-0.13) cm3 molecule(-1) s(-1) (220-363 K), and k(CCl3 + NO2) = (3.35 +/- 0.10) x 10(-12) (T/300 K)(-2.2+/-0.4) cm3 molecule(-1) s(-1) (298-363 K), with the uncertainties given as one-standard deviations. Estimated overall uncertainties in the measured bimolecular reaction rate coefficients are about +/-25%. In the reactions CH2Cl + NO2, CHCl2 + NO2, and CCl3 + NO2, the products observed are formaldehyde, CHClO, and phosgene (CCl2O), respectively. In addition, a weak signal for the HCl formation has been detected for the CHCl2 + NO2 reaction.
利用与光电离质谱仪相连的管式流动反应器，在220至360 K的温度下进行直接测量，研究了氯化甲基自由基（CH2Cl、CHCl2和CCl3）与NO2的反应动力学。通过对适当前驱体进行脉冲激光光解，在193或248 nm处均相产生自由基。在时间分辨测量中监测自由基浓度的衰减，以在NO2量大大超过自由基浓度的准一级条件下获得反应速率系数。所有三个反应的双分子速率系数在实验范围（1 - 6 Torr）内与缓冲气体（He或N2）和压力无关，并且发现其随温度的变化如下：k(CH2Cl + NO2) = (2.16 ± 0.08) x 10(-11) (T/300 K)(-1.12 ± 0.24) cm3 molecule(-1) s(-1) （220 - 363 K），k(CHCl2 + NO2) = (8.90 ± 0.16) x 10(-12) (T/300 K)(-1.48 ± 0.13) cm3 molecule(-1) s(-1) （220 - 363 K），以及k(CCl3 + NO2) = (3.35 ± 0.10) x 10(-12) (T/300 K)(-2.2 ± 0.4) cm3 molecule(-1) s(-1) （298 - 363 K），不确定性以一标准偏差给出。测量的双分子反应速率系数的估计总不确定性约为±25%。在反应CH2Cl + NO2、CHCl2 + NO2和CCl3 + NO2中，观察到的产物分别是甲醛、CHClO和光气（CCl2O）。此外，对于CHCl2 + NO2反应，检测到了微弱的HCl生成信号。
