Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu 30010, Taiwan.
1] Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu 30010, Taiwan [2] Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan.
Nat Chem. 2014 Jun;6(6):477-83. doi: 10.1038/nchem.1890. Epub 2014 Mar 23.
Criegee intermediates, which are carbonyl oxides produced when ozone reacts with unsaturated hydrocarbons, play an important role in the formation of OH and organic acids in the atmosphere, but they have eluded direct detection until recently. Reactions that involve Criegee intermediates are not understood fully because data based on their direct observation are limited. We used transient infrared absorption spectroscopy to probe directly the decay kinetics of formaldehyde oxide (CH2OO) and found that it reacts with itself extremely rapidly. This fast self-reaction is a result of its zwitterionic character. According to our quantum-chemical calculations, a cyclic dimeric intermediate that has the terminal O atom of one CH2OO bonded to the C atom of the other CH2OO is formed with large exothermicity before further decomposition to 2H2CO + O2((1)Δg). We suggest that the inclusion of this previously overlooked rapid reaction in models may affect the interpretation of previous laboratory experiments that involve Criegee intermediates.
Criegee 中间体是臭氧与不饱和烃反应时生成的羰基氧化物，它们在大气中 OH 和有机酸的形成中起着重要作用，但直到最近才被直接检测到。由于基于直接观察的数据有限，因此，涉及 Criegee 中间体的反应还不完全了解。我们使用瞬态红外吸收光谱法直接探测甲醛氧化物 (CH2OO) 的衰减动力学，发现它与自身反应非常迅速。这种快速的自反应是由于其两性离子特性所致。根据我们的量子化学计算，在进一步分解为 2H2CO + O2((1)Δg) 之前，具有一个 CH2OO 的末端 O 原子与另一个 CH2OO 的 C 原子键合的环状二聚体中间体以很大的放热形成。我们建议，在模型中包含这个以前被忽视的快速反应可能会影响以前涉及 Criegee 中间体的实验室实验的解释。
