The reaction mechanism for chlorine radical (^•Cl)-initiated atmospheric oxidation of dipropyl thiosulfinate (DPTS) in the gas phase was investigated using ab initio/density functional theory electronic structure calculations. The DPTS + ^•Cl reaction proceeds by H-abstraction and substitution pathways. The results indicate that the Cl radical adds to the S-atom of the sulfinyl [S(═O)] group of DPTS, which is followed by cleavage of the S(═O)–S single bond, leading to the formation of propanesulfinyl chloride and propanethiyl radical (PTR). The barrier height for this reaction was estimated to be −12.2 kcal mol^–1 relative to the separated starting reactants. The rate coefficients were calculated for all possible H-abstraction and substitution paths using the master equation solver for the multi-energy well reactions (MESMER) kinetic code in the atmospherically relevant temperature range of 200–300 K and at 1 atm pressure. The rate coefficient data for all reaction paths indicate that the formation of propanesulfinyl chloride and PTR from the DPTS + ^•Cl reaction is the major path. The rate coefficient for this reaction was estimated to be ∼6.00 × 10^–10 cm³ molecule^–1 s^–1 at 298 K and 1 atm pressure. The overall rate coefficient for the DPTS + ^•Cl reaction in the same temperature range was found to be ∼8.14 × 10^–10 cm³ molecule^–1 s^–1 at 298 K. The atmospheric lifetime of DPTS was calculated to be ∼3 h in the temperatures between 200 and 300 K and at 1 atm. In addition, the branching ratio fractions for each reaction were determined and the atmospheric implications are discussed. Overall, the results reveal that while the primary products of the DPTS + Cl radical reaction are short-lived, the compounds formed from their subsequent oxidative degradation do contribute to global warming and have the potential to exhibit adverse environmental impacts.

中文翻译：

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在气相中由 Cl 自由基引发的硫代亚磺酸二丙酯的氧化：对大气化学的影响

使用从头算/密度泛函理论电子结构计算研究了氯自由基 ( ^• Cl) 引发的硫代亚磺酸二丙酯 (DPTS) 在气相中的大气氧化反应机理。DPTS + ^• Cl 反应通过H-抽象和取代途径进行。结果表明，Cl 自由基与 DPTS 的亚磺酰基 [S(=O)] 基团的 S 原子相加，随后 S(=O)-S 单键断裂，导致丙亚磺酰基的形成氯和丙硫基自由基 (PTR)。该反应的势垒高度估计为 -12.2 kcal mol ^–1相对于分离的起始反应物。在 200-300 K 的大气相关温度范围和 1 个大气压下，使用多能井反应 (MESMER) 动力学代码的主方程求解器计算了所有可能的 H 抽象和取代路径的速率系数。所有反应路径的速率系数数据表明，DPTS + ^• Cl 反应生成丙亚磺酰氯和 PTR是主要路径。在 298 K 和 1 个大气压下，该反应的速率系数估计为 ~6.00 × 10 ^–10 cm ³分子^–1 s ^–1。DPTS 的总速率系数 + ^•发现在相同温度范围内的 Cl 反应在298 K 时为 ~ 8.14 × 10 ^–10 cm ³分子^–1 s ^–1。在 200 和 300 K 之间的温度下，计算出 DPTS 的大气寿命为 ~3 小时，并且在 1 个大气压。此外，确定了每个反应的支化比例，并讨论了大气影响。总体而言，结果表明，虽然 DPTS + Cl 自由基反应的主要产物寿命很短，但随后氧化降解形成的化合物确实会导致全球变暖，并有可能对环境产生不利影响。