The role of water in gas-phase reactions has gained considerable interest. Here we report a direct kinetic measurement of the reaction of syn-CH₃CHOO (a Criegee intermediate or carbonyl oxide) with methanol at various relative humidity (RH = 0–80%) under near-ambient conditions (298 K, 250–755 Torr). The data indicate that a single water molecule expedites the reaction by up to a factor of three. The rate coefficient of the corresponding reaction, syn-CH₃CHOO + CH₃OH + H₂O → products, has been determined to be (1.95 ± 0.11) × 10^–32 cm⁶ s^–1 at 298 K, with no observable pressure dependence for 250–755 Torr. Quantum chemistry calculation shows that the dominating pathway involves a hydrogen-bonded ring structure, in which methanol is donating a hydrogen atom to water, water is donating a hydrogen atom to the terminal oxygen atom of the Criegee intermediate, and, on the product side, H₂O is reformed and acts as a catalyst.

中文翻译：

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单一水分子增强了Criegee与酒精的中间反应

水在气相反应中的作用已引起人们极大的兴趣。在这里，我们报告了在接近室温（298 K，250-755）的各种相对湿度（RH = 0–80％）下，syn -CH ₃ CHOO（一种Criegee中间体或羰基氧化物）与甲醇反应的直接动力学测量。r）。数据表明单个水分子最多可将反应速度提高三倍。相应反应的速率系数syn -CH ₃ CHOO + CH ₃ OH + H ₂ O→产物已确定为（1.95±0.11）×10 ^–32 cm ⁶ s ^–1在298 K时，对于250–755 Torr没有明显的压力依赖性。量子化学计算表明，主要途径涉及氢键合的环结构，其中甲醇将氢原子提供给水，水将氢原子提供给Criegee中间体的末端氧原子，在产物侧， H ₂ O被重整并充当催化剂。