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.
Department of Chemistry, Louisiana State University, Baton Rouge, LA 12222, United States.
J Phys Chem A. 2024 Oct 17;128(41):8983-8995. doi: 10.1021/acs.jpca.4c05428. Epub 2024 Oct 8.
Chloroprene (CP; CH═C(Cl)-CH═CH) is a significant toxic airborne pollutant, often originating from anthropogenic activities. However, the environmental fate of CP is incompletely understood. High level CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ calculations combined with kinetic modeling were employed here to glean new insight into the reaction mechanism, energies, and kinetics of the reaction of CP with OH radical (OH). We report the energies of four different addition pathways and six different abstraction pathways. The OH attack on the terminal C atom of the =CH group (which is directly attached to the =CCl moiety), leading to the formation of HOCH-C(Cl)-CH═CH, was found to be a major path. The barrier height for the formation of the corresponding transition state was found to be -1.9 kcal mol below that of the starting CP + OH reactants. Rate coefficients were calculated for addition and abstraction pathways involving the CP + OH reaction under pre-equilibrium approximation conditions, employing a combination of canonical variational transition state theory and small curvature tunneling. The overall rate coefficient for the reaction of CP + OH at 298 K was found to be 1.4 × 10 cm molecule s. The thermochemistry of the possible channels and atmospheric implications are provided. In addition, the fate of HOCH-C(Cl)-CH═CH in the presence of O was investigated. We found the reaction of the CP-derived peroxy radical adduct with HO and NO to make contributions to the formation of products such as formaldehyde, HO radical, Cl atom, HOCHC(OOH)(Cl)CH═CH, HOCHC(O)Cl, ClC(O)CH═CH, HOCHC(O)CH═CH, and HC(O) radical.
氯丁二烯（CP；CH═C(Cl)-CH═CH）是一种重要的有毒空气污染物，通常源自人为活动。然而，人们对CP在环境中的归宿了解并不完全。本文采用高水平的CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ计算方法并结合动力学模型，以深入了解CP与羟基自由基（OH）反应的机理、能量和动力学。我们报告了四种不同加成途径和六种不同夺氢途径的能量。发现OH进攻=CH基团的末端C原子（该C原子直接连接到=CCl部分），生成HOCH-C(Cl)-CH═CH，是主要反应路径。发现形成相应过渡态的势垒高度比起始CP + OH反应物的势垒高度低1.9 kcal mol。在预平衡近似条件下，采用正则变分过渡态理论和小曲率隧道效应相结合的方法，计算了涉及CP + OH反应的加成和夺氢途径的速率系数。发现CP + OH在298 K时反应的总速率系数为1.4 × 10 cm molecule s。提供了可能反应通道的热化学性质及其大气影响。此外，还研究了在有O存在的情况下HOCH-C(Cl)-CH═CH的归宿。我们发现CP衍生的过氧自由基加合物与HO和NO的反应有助于生成甲醛、HO自由基、Cl原子、HOCHC(OOH)(Cl)CH═CH、HOCHC(O)Cl、ClC(O)CH═CH、HOCHC(O)CH═CH和HC(O)自由基等产物。
