Spin-Trapping Evidence for the Formation of Alkyl, Alkoxyl, and Alkylperoxyl Radicals in the Reactions of Dialkylzincs with Oxygen
作者:Julien Maury、Laurence Feray、Samantha Bazin、Jean-Louis Clément、Sylvain R. A. Marque、Didier Siri、Michèle P. Bertrand
DOI:10.1002/chem.201002616
日期:2011.2.1
and nBu2Zn) with oxygen have been investigated by EPR spectroscopy using spin‐trapping techniques. The use of 5‐diethoxyphosphoryl‐5‐methyl‐1‐pyrrroline N‐oxide (DEPMPO) as a spin‐trap has allowed the involvement of alkyl, alkylperoxyl, and alkoxyl radicals in this process to be probed for the first time. The relative ratio of the corresponding spin‐adducts depends strongly on the nature of the R group
通过使用自旋捕集技术的EPR光谱研究了二烷基锌(Me 2 Zn,Et 2 Zn和n Bu 2 Zn)与氧气的反应。使用5-二乙氧基磷酰基-5-甲基-1-吡咯啉N-氧化物(DEPMPO)作为自旋捕集阱,首次探究了该过程中烷基,烷基过氧基和烷氧基的参与。相应的自旋加合物的相对比例在很大程度上取决于控制CZn键解离焓的R基团的性质,以及实验条件(与R 2 Zn相比,自旋阱数量过多,反之亦然)。结果表明,Et 2Zn和n Bu 2 Zn在较小程度上是氧中心物种的陷阱,比Me 2 Zn好得多。当相对于自旋捕集器过量使用二烷基锌时,对于Et 2 Zn和n Bu 2 Zn ,DEPMPO的以氧为中心的自由基加合物的浓度比对Me 2 Zn低得多。详细的反应机理进行了讨论和C 锌,O- 的Zn和O 在UB3LYP / 6-311 ++ G(3DF,3PD)分别计算所提出的反应中间体O键离解焓// UB3LYP