Formation of a Resonance-Stabilized Radical Intermediate by Hydroxyl Radical Addition to Cyclopentadiene
Formation of a Resonance-Stabilized Radical Intermediate by Hydroxyl Radical Addition to Cyclopentadiene
复制标题
通过羟基自由基加成环戊二烯形成共振稳定的自由基中间体
DOI：
10.1021/acs.jpca.2c06934
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Goulay, Fabien
中科院分区：
文献类型：
--
作者：
Caster, Kacee L.;Lee, James;Donnellan, Zachery;Selby, Talitha M.;Osborn, David L.;Goulay, Fabien
在室温下，用多重光电离质谱研究了OH自由基与环戊二烯（C5H6）的反应。OH自由基在其基础电子状态下产生的气相中通过248 nm的光解H2O2或351 nm的光解HONO。光离子光谱和时间分布的分析表明，在室温下，在4 - 8托的压力范围内，共振稳定的5-羟基环戊二烯-2-烯-1-基（C5H6OH）是主要观察到的反应产物。未检测到提取产物（C5H5）。在CCSD（T）/cc-pVTZ//M06 - 2X/6 - 311 ++ G ** 水平上计算的C5H6OH势能面表明，OH自由基与环戊二烯的π体系无势垒加成形成货车范德华络合物，形成共振稳定的自由基产物.这种弱结合的加合物通过浸没的能垒异构化为共振稳定的加成加合物。主方程计算，包括两个OH-加成入口途径，预测5-羟基环戊二烯-2-烯-1-基仍然是唯一的加成产物高达500 K。在室温下检测到含OH的共振稳定自由基进一步突出了它们在富碳和富氧环境中的重要性，如燃烧，行星大气和星际介质。
The reaction of the OH radical with cyclopentadiene (C5H6) was investigated at room temperature using multiplexed photoionization mass spectrometry. OH radicals in their ground electronic state were generated in the gas phase by 248 nm photolysis of H2O2or 351 nm photolysis of HONO. Analysis of photoion spectra and temporal profiles reveal that at room temperature and over the 4–8 Torr pressure range, the resonance-stabilized 5-hydroxycyclopent-2-en-1-yl (C5H6OH) is the main observed reaction product. Abstraction products (C5H5) were not detected. The C5H6OH potential energy surface calculated at the CCSD(T)/cc-pVTZ//M06-2X/6-311++G** level of theory suggests that the resonance-stabilized radical product is formed through barrierless addition of the OH radical onto cyclopentadiene’s π system to form a van der Waals complex. This weakly bound adduct isomerizes through a submerged energy barrier to the resonance-stabilized addition adduct. Master Equation calculations, including two OH-addition entrance pathways, predict that 5-hydroxycyclopent-2-en-1-yl remains the sole addition product up to 500 K. The detection of an OH-containing resonance-stabilized radical at room temperature further highlights their importance in carbon- and oxygen-rich environments such as combustion, planetary atmospheres, and the interstellar medium.