Infrared Absorption Spectrum of the Simplest Criegee Intermediate CH
<sub>2</sub>
OO
作者:Yu-Te Su、Yu-Hsuan Huang、Henryk A. Witek、Yuan-Pern Lee
DOI:10.1126/science.1234369
日期:2013.4.12
bears a methyl group in place of one of the hydrogenatoms. The vibrational spectrum of an intermediate involved in ozone chemistry may facilitate its direct study in the atmosphere. [Also see Perspective by Vereecken] The Criegee intermediates are carbonyl oxides postulated to play key roles in the reactions of ozone with unsaturated hydrocarbons; these reactions constitute an important mechanism for the
Kinetic study of the CH<sub>3</sub>O<sub>2</sub> + Br reaction at 298 K
作者:A. Aranda、G. Laverdet、G. Le Bras、G. Poulet
DOI:10.1051/jcp:1998224
日期:1998.5
The kinetics and mechanism of the reaction CH3O2 + Br → products (1) have been studied at 298 K using the discharge flow method with detection of species by mass spectrometry. The rate constant obtained is: k1 = (4.4±0.4)×10-13 cm3 molecule-1 s-1. The major and likely unique channel leads to the formation of BrO. These results, which are the first ones for this reaction, are compared with those of the CH3O2 + Cl reaction.
The ozonolysis of vinyl ethers (1a,b) in the presence of thioadamantan-2-one (4a) gave in each case the corresponding thin-ozonide (5a,b) in around 70% yield, whilst ozonolysis of a mixture of vinyl ethers (1a—c) and thiobenzophenone derivatives (4b—d) gave the corresponding thione-S-oxides (8b—d) in 15–30% yields, together with the benzophenones (6b—d).
Ultraviolet Spectrum and Photochemistry of the Simplest Criegee Intermediate CH<sub>2</sub>OO
作者:Joseph M. Beames、Fang Liu、Lu Lu、Marsha I. Lester
DOI:10.1021/ja310603j
日期:2012.12.12
Ozonolysis of alkenes in the troposphere produces Criegee intermediates, which have eluded detection in the gas phase until very recently. This laboratory has synthesized the simplest Criegee intermediate within a quartz capillary tube affixed to a pulsed valve to cool and isolate CH(2)OO in a supersonic expansion. UV excitation resonant with the B (1)A' ← X (1)A' transition depletes the ground-state
对流层中烯烃的臭氧分解产生 Criegee 中间体,直到最近才在气相中检测到。该实验室在石英毛细管内合成了最简单的 Criegee 中间体,该石英毛细管固定在脉冲阀上,以在超音速膨胀中冷却和隔离 CH(2)OO。与 B (1)A' ← X (1)A' 跃迁共振的 UV 激发会耗尽 CH(2)OO 的基态群,其可通过 118 nm 的单光子电离检测到。335 nm 处的轮廓峰值附近的大量紫外线引起的损耗(接近 100%)表明快速解离,这与理论上计算的沿 OO 坐标的排斥性 B (1)A' 电位一致。实验光谱与利用一维反射原理计算得到的吸收光谱非常吻合。
Extremely rapid self-reaction of the simplest Criegee intermediate CH2OO and its implications in atmospheric chemistry
作者:Yu-Te Su、Hui-Yu Lin、Raghunath Putikam、Hiroyuki Matsui、M. C. Lin、Yuan-Pern Lee
DOI:10.1038/nchem.1890
日期:2014.6
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 2H2COÂ +Â O2(1Îg). 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 intermediates play an important role in atmospheric chemistry but their direct study has proved difficult. Transient infrared absorption spectroscopy has now been used to probe the decay kinetics of the Criegee intermediate CH2OO directly, revealing that its self-reaction is extremely rapid. This may have important consequences for the interpretation of previous laboratory experiments.
克里基中间物是臭氧与不饱和碳氢化合物反应时产生的羰基氧化物,在大气中形成 OH 和有机酸的过程中发挥着重要作用,但直到最近才被直接检测到。由于基于直接观测的数据有限,人们对涉及克里基中间体的反应还不完全了解。我们利用瞬态红外吸收光谱直接探测了氧化甲醛(CH2OO)的衰变动力学,发现它与自身的反应速度极快。这种快速的自我反应是其具有齐聚离子特性的结果。根据我们的量子化学计算,在进一步分解为 2H2COÂ +Â O2(1δg)之前,会形成一个环状二聚中间体,其中一个 CH2OO 的末端 O 原子与另一个 CH2OO 的 C 原子成键,放热很大。我们认为,在模型中加入这种以前被忽视的快速反应可能会影响对以前涉及克里基中间体的实验室实验的解释。克里基中间产物在大气化学中发挥着重要作用,但对它们的直接研究却很困难。现在,我们利用瞬态红外吸收光谱直接探测了克里基中间体 CH2OO 的衰变动力学,发现它的自我反应非常迅速。这可能会对解释以前的实验室实验产生重要影响。