Product Branching Fractions of the CH + Propene Reaction from Synchrotron Photoionization Mass Spectrometry

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• 作者：Adam J. Trevitt ; Matthew B. Prendergast ; Fabien Goulay ; John D. Savee ; David L. Osborn ; Craig A. Taatjes ; Stephen R. Leone
• 刊名：The Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：August 1, 2013
• 年：2013
• 卷：117
• 期：30
• 页码：6450-6457
• 全文大小：328K
• 年卷期：v.117,no.30(August 1, 2013)
• ISSN：1520-5215

文摘

The CH(X²螤) + propene reaction is studied in the gas phase at 298 K and 4 Torr (533.3 Pa) using VUV synchrotron photoionization mass spectrometry. The dominant product channel is the formation of C₄H₆ (m/z 54) + H. By fitting experimental photoionization spectra to measured spectra of known C₄H₆ isomers, the following relative branching fractions are obtained: 1,3-butadiene (0.63 卤 0.13), 1,2-butadiene (0.25 卤 0.05), and 1-butyne (0.12 卤 0.03) with no detectable contribution from 2-butyne. The CD + propene reaction is also studied and two product channels are observed that correspond to C₄H₆ (m/z 54) + D and C₄H₅D (m/z 55) + H, formed at a ratio of 0.4 (m/z 54) to 1.0 (m/z 55). The D elimination channel forms almost exclusively 1,2-butadiene (0.97 卤 0.20) whereas the H elimination channel leads to the formation of deuterated 1,3-butadiene (0.89 卤 0.18) and 1-butyne (0.11 卤 0.02); photoionization spectra of undeuterated species are used in the fitting of the measured m/z 55 (C₄H₅D) spectrum. The results are generally consistent with a CH cycloaddition mechanism to the C鈺怌 bond of propene, forming 1-methylallyl followed by elimination of a H atom via several competing processes. The direct detection of 1,3-butadiene as a reaction product is an important validation of molecular weight growth schemes implicating the CH + propene reaction, for example, those reported recently for the formation of benzene in the interstellar medium (Jones, B. M. Proc. Natl. Acad. Sci. U.S.A. 2011, 108, 452鈭?57).