We report the first direct kinetic measurements of a cyclic stabilized Criegee Intermediate. We have measured the unimolecular reaction rate coefficient of cyclohexanone oxide (c-(CH₂)₅COO) in the temperature 213–296 K and pressure 7–50 Torr ranges using absorption spectrometry. The c-(CH₂)₅COO was produced by the photolysis of c-(CH₂)₅CIBr at 213 nm in the presence of O₂. We compare the measured fast c-(CH₂)₅COO unimolecular rate coefficient, 1998 ± 147 s^–1 at 296 K, with the literature calculations for the structurally similar E-nopinone oxide formed in β-pinene ozonolysis. The k_uni(c-(CH₂)₅COO)/k_uni(E-nopinone oxide) ratio calculated using transition-state theory and density functional theory agrees well with this comparison. We have also measured the bimolecular rate coefficient of the reaction between c-(CH₂)₅COO and trifluoroacetic acid at 253 K and 10 Torr and obtained the value (8.7 ± 1.0) × 10^–10 cm³ molecule^–1 s^–1. This very large value agrees with previous kinetic measurements for reactions between stabilized Criegee intermediates and halogenated organic acids.

中文翻译：

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循环 Criegee 中间体的直接动力学测量； c-(CH2)5COO的单分子分解


我们报告了循环稳定 Criegee 中间体的首次直接动力学测量。我们使用吸收光谱法测量了环己酮氧化物 (c-(CH ₂ ) ₅ COO) 在温度 213–296 K 和压力 7–50 Torr 范围内的单分子反应速率系数。 c-(CH ₂ ) ₅ COO 由 c-(CH ₂ ) ₅ CIBr 在 213 nm 光解产生在 O ₂ 存在的情况下。我们将 296 K 下测得的快速 c-(CH ₂ ) ₅ COO 单分子速率系数 (1998 ± 147 s ^–1 ) 与文献计算值进行比较β-蒎烯臭氧分解中形成结构相似的 E-nopinone 氧化物。使用过渡计算得出的 k _uni (c-(CH ₂ ) ₅ COO)/k _uni (E-诺蒎酮氧化物) 比率-状态理论和密度泛函理论与这种比较非常吻合。我们还测量了 c-(CH ₂ ) ₅ COO 与三氟乙酸在 253 K、10 Torr 下反应的双分子速率系数，得出值 (8.7 ± 1.0) × 10 ^–10 cm ³ 分子 ^–1 s ^–1 。这个非常大的值与之前稳定的 Criegee 中间体和卤代有机酸之间反应的动力学测量结果一致。