Lin Liang-Chun, Chao Wen, Chang Chun-Hung, Takahashi Kaito, Lin Jim Jr-Min
Institute of Atomic and Molecular Sciences, Academia Sinica, No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan.
Phys Chem Chem Phys. 2016 Oct 12;18(40):28189-28197. doi: 10.1039/c6cp05171e.
The kinetics of the reaction of anti-CHCHOO with water vapor were investigated using transient UV absorption spectroscopy at temperatures from 288 to 328 K and 500 Torr. We found that both the water monomer and the water dimer react with anti-CHCHOO. The rate coefficients of the reaction of the water monomer and dimer with anti-CHCHOO at 298 K were determined to be (1.31 ± 0.26) × 10 cm s and (4.40 ± 0.29) × 10 cm s, respectively. Furthermore, for the water dimer reaction, we observed very large negative temperature dependence with an activation energy of -12.17 ± 0.66 kcal mol. On the other hand, the monomer reaction showed minimal temperature dependence with nearly zero activation energy. At atmospherically relevant humidity, in opposition to previous experiments conducted for CHOO in which water dimer reaction predominates at room temperature, for anti-CHCHOO, the water monomer reaction can contribute significantly (∼30% of the reaction with water vapor at relative humidity RH = 40% and 298 K). These results show that substitution of an alkyl group can greatly affect the reaction of Criegee intermediates with water vapor, especially changing the contributions of water monomer and dimer reactions.
在288至328 K温度和500托压力条件下，采用瞬态紫外吸收光谱法研究了反式-CHCHOO与水蒸气反应的动力学。我们发现，水单体和水二聚体均与反式-CHCHOO发生反应。在298 K时，水单体和水二聚体与反式-CHCHOO反应的速率系数分别测定为(1.31±0.26)×10 cm³ s⁻¹和(4.40±0.29)×10 cm³ s⁻¹。此外，对于水二聚体反应，我们观察到非常大的负温度依赖性，活化能为-12.17±0.66 kcal mol⁻¹。另一方面，单体反应显示出最小的温度依赖性，活化能几乎为零。在与大气相关的湿度条件下，与之前对CHOO进行的实验不同，在之前的实验中，水二聚体反应在室温下占主导，而对于反式-CHCHOO，水单体反应的贡献可能很大（在相对湿度RH = 40%和298 K时，约占与水蒸气反应的30%）。这些结果表明，烷基的取代会极大地影响Criegee中间体与水蒸气的反应，特别是改变水单体和水二聚体反应的贡献。
