Arathala Parandaman, Musah Rabi A
Department of Chemistry, University at Albany─State University of New York, 1400 Washington Avenue, Albany, New York 12222, United States.
J Phys Chem A. 2022 Jul 7;126(26):4264-4276. doi: 10.1021/acs.jpca.2c01203. Epub 2022 Jun 27.
The thermochemistry and kinetics of the atmospheric oxidation mechanism for propanesulfinyl chloride (CH-CH-CH-S(═O)Cl; PSICl) initiated by the hydroxyl (OH) radical were investigated with high level quantum chemistry calculations and the Master equation solver for multi-energy well reaction (Mesmer) kinetic code. The mechanism for the oxidation of PSICl in the presence of OH radical can proceed via H-abstraction and substitution pathways. The CCSD(T)/aug-cc-pV(T+d)Z//MP2/aug-cc-pV(T+d)Z level calculated energies revealed addition of the OH radical to the S-atom of the sulfinyl (-S(═O)) moiety, followed by cleavage of the Cl-S(═O) single bond, leading to formation of propanesulfinic acid (PSIA) and the Cl radical to be the major pathway when compared to all other possible channels. The transition state barrier height for this reaction was found to be -3.0 kcal mol relative to the energy of the starting PSICl + OH radical reactants. The rate coefficients were calculated for all possible paths in the atmospherically relevant temperature range of 200-320 K and at 1 atm. The rate coefficient for the formation of the PSIA + Cl radical from the PSICl + OH radical reaction was found to be 8.2 × 10 cm molecule s at 298 K and a pressure of 1 atm. From branching ratio calculations, it was revealed that the reaction resulting in the formation of the PSIA + Cl radical contributed ∼52% to the total reaction. The overall rate coefficient for the PSICl + OH reaction was also calculated and found to be 1.6 × 10 cm molecule s at 298 K and a pressure of 1 atm. In the aggregate, the results indicate the atmospheric lifetime of PSICl to be ∼12-20 h in the temperature range between 200 and 320 K, which suggests that its contribution to global warming is negligible. However, the degradation products revealed to be formed in its interactions with the OH radical, which include that SO, Cl radical, HO radical, and propylene have significant effects on the formation of acid rain, secondary organic aerosols, the ozone layer, and global warming.
通过高水平量子化学计算和多能阱反应主方程求解器（Mesmer）动力学代码，研究了由羟基（OH）自由基引发的丙烷亚磺酰氯（CH₃CH₂CH₂S(═O)Cl；PSICl）大气氧化机制的热化学和动力学。在OH自由基存在下，PSICl的氧化机制可通过氢原子夺取和取代途径进行。CCSD(T)/aug-cc-pV(T+d)Z//MP2/aug-cc-pV(T+d)Z水平计算的能量表明，OH自由基加成到亚磺酰基（-S(═O)）部分的S原子上，随后Cl-S(═O)单键断裂，与所有其他可能的通道相比，这导致形成丙烷亚磺酸（PSIA）和Cl自由基是主要途径。发现该反应的过渡态势垒高度相对于起始PSICl + OH自由基反应物的能量为-3.0 kcal mol⁻¹。在200 - 320 K的大气相关温度范围和1 atm压力下，计算了所有可能路径的速率系数。发现PSICl + OH自由基反应形成PSIA + Cl自由基的速率系数在298 K和1 atm压力下为8.2×10⁻¹² cm³ molecule⁻¹ s⁻¹。通过分支比计算表明，导致形成PSIA + Cl自由基的反应占总反应的约52%。还计算了PSICl + OH反应的总速率系数，发现在298 K和1 atm压力下为1.6×10⁻¹¹ cm³ molecule⁻¹ s⁻¹。总体而言，结果表明在200至320 K的温度范围内，PSICl的大气寿命约为12 - 20小时，这表明其对全球变暖的贡献可忽略不计。然而，其与OH自由基相互作用形成的降解产物，包括SO、Cl自由基、HO自由基和丙烯，对酸雨、二次有机气溶胶、臭氧层和全球变暖的形成有显著影响。
