15819-00-8Relevant academic research and scientific papers
Spin-trapping evidence for the formation of alkyl, alkoxyl, and alkylperoxyl radicals in the reactions of dialkylzincs with oxygen
Maury, Julien,Feray, Laurence,Bazin, Samantha,Clement, Jean-Louis,Marque, Sylvain R. A.,Siri, Didier,Bertrand, Michele P.
, p. 1586 - 1595 (2011)
The reactions of dialkylzincs (Me2Zn, Et2Zn, 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, which controls the C-Zn bond dissociation enthalpy, and on the experimental conditions (excess of spin-trap compared with R 2Zn and vice versa). The results have demonstrated that Et 2Zn and, to a lesser extent, nBu2Zn are much better traps for oxygen-centered species than Me2Zn. When the dialkylzincs were used in excess with respect to the spin-trap, the concentration of the oxygen-centered radical adducts of DEPMPO was much lower for Et2Zn and nBu2Zn than for Me2Zn. A detailed reaction mechanism is discussed and C-Zn, O-Zn, and O-O bond dissociation enthalpies for the proposed reaction intermediates were calculated at the UB3LYP/6-311++G(3df,3pd)/ /UB3LYP/6-31G(d,p) level of theory to support the rationale. All trapped! The reactions of dialkylzincs with oxygen (see scheme) have been investigated with EPR spectroscopy by using spin-trapping techniques. The use of 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. A detailed mechanism is discussed in the light of theoretical calculations of the C-Zn, O-Zn, and O-O bond dissociation enthalpies of the proposed reaction intermediates.
