Cardona Alejandro L, Rivela Cynthia B, Gibilisco Rodrigo G, Blanco María Belén, Ventura Oscar N, Teruel Mariano
(L.U.Q.C.A), Laboratorio Universitario de Química y Contaminación del Aire, Instituto de Investigaciones en Fisicoquímica de Córdoba (I.N.F.I.Q.C.), Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
Institute for Atmospheric and Environmental Research, Faculty for Mathematics and Natural Sciences, University of Wuppertal, D-42097 Wuppertal, Germany.
J Phys Chem A. 2022 Sep 29;126(38):6751-6761. doi: 10.1021/acs.jpca.2c04547. Epub 2022 Sep 16.
Rate coefficients of the O-initiated oxidation of allyl methyl sulfide (HC═CHCHSCH, AMS) and allyl ethyl sulfide (HC═CHCHSCHCH, AES) were determined at atmospheric conditions by "in situ" FTIR. The relative kinetic experiments were performed using methylcyclohexane (McH) and carbon monoxide (CO) as nascent OH radical scavengers and in the absence of any scavenger, to determine the impact that the formation of OH radicals has on the rate coefficients. In the absence of scavengers, values of = (5.23 ± 3.57) × 10 and = (5.76 ± 1.80) × 10 cm molecule s were obtained. In the presence of the scavengers, however, the rates decreased to = (3.92 ± 1.92) × 10 and = (2.63 ± 0.47) × 10 cm molecule s for AMS, and = (4.78 ± 1.38) × 10 and = (3.50 ± 0.27) × 10 cm molecule s for AES. On the basis of these results, we have decided to recommend the values obtained using CO as scavenger as those best representing the rate coefficient for the reactions of O with AMS and AES. The reaction mechanism was explored using DFT and post-Hartree-Fock computational methods. It is shown that the barrier for the common cyclization to primary ozonide (-3.7 ± 0.1 kcal mol) followed by other reactions, as well as that for the reaction with the sulfur atom (-5.1 ± 0.1 kcal mol), is small and quite close, meaning that both reaction paths should contribute significantly to the global reaction rate.
在大气条件下，通过“原位”傅里叶变换红外光谱（FTIR）测定了烯丙基甲基硫醚（HC═CHCH₂SCH₃，AMS）和烯丙基乙基硫醚（HC═CHCH₂SCH₂CH₃，AES）的O引发氧化反应速率系数。使用甲基环己烷（McH）和一氧化碳（CO）作为新生OH自由基清除剂，并在不存在任何清除剂的情况下进行了相对动力学实验，以确定OH自由基的形成对反应速率系数的影响。在不存在清除剂的情况下，得到的速率系数值分别为(5.23 ± 3.57) × 10⁻¹¹和(5.76 ± 1.80) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹。然而，在存在清除剂的情况下，AMS的反应速率降至(3.92 ± 1.92) × 10⁻¹¹和(2.63 ± 0.47) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹，AES的反应速率降至(4.78 ± 1.38) × 10⁻¹¹和(3.50 ± 0.27) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹。基于这些结果，我们决定推荐使用CO作为清除剂时获得的值，作为最能代表O与AMS和AES反应速率系数的值。使用密度泛函理论（DFT）和后哈特里-福克计算方法探索了反应机理。结果表明，生成初级臭氧化物的常见环化反应（-3.7 ± 0.1 kcal mol⁻¹）以及随后的其他反应的势垒，与和硫原子反应的势垒（-5.1 ± 0.1 kcal mol⁻¹）都很小且非常接近，这意味着这两条反应路径都应对整体反应速率有显著贡献。
