Radical Reactivity in the Condensed Phase: Intermolecular versus Intramolecular Reactions of Alkoxy Radicals

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• 作者：Anthony J. Carrasquillo ; Kelly E. Daumit ; Jesse H. Kroll
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2015
• 出版时间：June 18, 2015
• 年：2015
• 卷：6
• 期：12
• 页码：2388-2392
• 全文大小：314K
• ISSN：1948-7185

文摘

Condensed-phase alkoxy (RO) radicals can undergo unimolecular (e.g., intramolecular H atom abstraction) reactions as well as bimolecular (intermolecular H atom abstraction) reactions, though the competition between these two channels is not well constrained. Here, we examine this branching by generating RO radicals from the photolysis of a large alkyl nitrite (C₂₀H₄₁ONO) in hexanes and nebulizing the mixture into an aerosol mass spectrometer for analysis. Product ions associated with unimolecular (isomerization) reactions were observed to increase upon photolysis. However, no formation of the C₂₀ alcohol (C₂₀H₄₁OH, the expected product from RO + RH reactions) was observed, suggesting that bimolecular reactions are at most a minor channel for this condensed-phase system (involving saturated hydrocarbons). This result, combined with previous studies of liquid-phase RO radicals carried out at higher concentrations, suggests that when 1,5-H atom abstraction reactions are facile (i.e., in which a 1,5-H atom shift from a secondary or tertiary carbon can occur), this channel will dominate over bimolecular reactions.