The atmospheric oxidation mechanism and energetics of propanesulfinic acid (CH₃CH₂CH₂S(O)OH, PSIA) initiated by OH radicals have been investigated at the CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ level of theory. The PSIA + ^•OH reaction proceeds through (i) H-atom abstraction and (ii) ^•OH addition pathways. The calculated energies indicate that the barrier height for the abstraction of H-atom from the −OH moiety of PSIA leading to the formation of CH₃CH₂CH₂S(O)₂ + H₂O is estimated to be −4.7 kcal mol^–1 relative to that of the separated reactants. The rate coefficients were determined for all possible reaction paths by RRKM-ME calculations using Master equation solver for multienergy well reactions (Mesmer) code in the atmospherically relevant temperatures between 200 and 320 K and bath gas pressures between 0.1 and 10 atm. The calculated bimolecular rate coefficients suggest that the formation of CH₃CH₂CH₂S(O)₂ + H₂O is predominant compared to the other possible reaction paths in the studied temperature range. The total rate coefficient for the PSIA + ^•OH reaction was found to be ∼8.40 × 10^–11 cm³ molecule^–1 s^–1 at T = 298 K and P = 1 atm. In addition, branching ratios, thermochemical parameters, atmospheric lifetime, and global warming potentials were determined. Overall, the results indicate that the atmospheric removal of PSIA with ^•OH results in the formation of sulfur dioxide (SO₂) from C–S single bond fission in the CH₃–CH₂–CH₂–S(O)₂ radical, which is formed by H-atom abstraction from the OH group of PSIA. Thus, the SO₂ product does not originate from the direct elimination of SO₂ from unimolecular dissociation of PSIA. The formed SO₂, propylene (C₃H₆), sulfurous acid (H₂SO₃), and hydroperoxyl (HO₂) radical are major products that may contribute to global warming and aerosol formation.

中文翻译：

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由 OH 自由基引发的丙亚磺酸的大气氧化：反应机理、能量学、速率系数和大气影响

在CCSD(T)/aug-cc-pVTZ//M06-2X/aug上研究了OH自由基引发的丙亚磺酸(CH ₃ CH ₂ CH ₂ S(O)OH, PSIA)的大气氧化机理和能量学-cc-pVTZ 理论水平。PSIA + ^• OH 反应通过 (i) H 原子提取和 (ii) ^• OH 添加途径进行。计算的能量表明，从 PSIA 的 -OH 部分提取 H 原子导致形成 CH ₃ CH ₂ CH ₂ S(O) ₂ + H ₂ O的势垒高度估计为 -4.7 kcal mol ^–1相对于分离的反应物。在 200 至 320 K 之间的大气相关温度和 0.1 至 10 个大气压之间的浴气压力下，使用多能井反应的主方程求解器 (Mesmer) 代码，通过 RRKM-ME 计算确定所有可能反应路径的速率系数。计算出的双分子速率系数表明，在研究的温度范围内，与其他可能的反应路径相比，CH ₃ CH ₂ CH ₂ S(O) ₂ + H ₂ O 的形成占主导地位。发现PSIA + ^• OH 反应的总速率系数为~8.40 × 10 ^–11 cm ³分子^–1s ^–1在T = 298 K 和P = 1 atm。此外，还确定了支化率、热化学参数、大气寿命和全球变暖潜势。总体而言，结果表明，使用^• OH大气去除 PSIA导致CH ₃ -CH ₂ -CH ₂ -S(O) ₂自由基中的C-S 单键裂变形成二氧化硫 (SO ₂ ) ，它是通过从 PSIA 的 OH 基团中提取 H 原子形成的。因此，SO ₂产物不是源自从PSIA的单分子解离直接消除SO ₂。形成的 SO ₂、丙烯 (C ₃ H ₆ )、亚硫酸 (H ₂ SO ₃ ) 和过氧化氢 (HO ₂ ) 自由基是可能导致全球变暖和气溶胶形成的主要产物。