Product Detection of the CH Radical Reaction with Acetaldehyde

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• 作者：Fabien Goulay ; Adam J. Trevitt ; John D. Savee ; Jordy Bouwman ; David L. Osborn ; Craig A. Taatjes ; Kevin R. Wilson ; Stephen R. Leone
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：June 21, 2012
• 年：2012
• 卷：116
• 期：24
• 页码：6091-6106
• 全文大小：616K
• 年卷期：v.116,no.24(June 21, 2012)
• ISSN：1520-5215

文摘

The reaction of the methylidyne radical (CH) with acetaldehyde (CH₃CHO) is studied at room temperature and at a pressure of 4 Torr (533.3 Pa) using a multiplexed photoionization mass spectrometer coupled to the tunable vacuum ultraviolet synchrotron radiation of the Advanced Light Source at Lawrence Berkeley National Laboratory. The CH radicals are generated by 248 nm multiphoton photolysis of CHBr₃ and react with acetaldehyde in an excess of helium and nitrogen gas flow. Five reaction exit channels are observed corresponding to elimination of methylene (CH₂), elimination of a formyl radical (HCO), elimination of carbon monoxide (CO), elimination of a methyl radical (CH₃), and elimination of a hydrogen atom. Analysis of the photoionization yields versus photon energy for the reaction of CH and CD radicals with acetaldehyde and CH radical with partially deuterated acetaldehyde (CD₃CHO) provides fine details about the reaction mechanism. The CH₂ elimination channel is found to preferentially form the acetyl radical by removal of the aldehydic hydrogen. The insertion of the CH radical into a C鈥揌 bond of the methyl group of acetaldehyde is likely to lead to a C₃H₅O reaction intermediate that can isomerize by 尾-hydrogen transfer of the aldehydic hydrogen atom and dissociate to form acrolein + H or ketene + CH₃, which are observed directly. Cycloaddition of the radical onto the carbonyl group is likely to lead to the formation of the observed products, methylketene, methyleneoxirane, and acrolein.