Factors affecting the relative and absolute rates of ß-scission of alkoxythiocarbonyl radicals and alkoxycarbonyl radicals

Abstract : High-level ab initio calculations demonstrate that alkoxythiocarbonyl radicals (ROC.=S) undergo ß-scission significantly faster than alkoxycarbonyl radicals (ROC.=O) despite having similar exothermicities. The relatively low reactivity of the ROC.=O radicals is reduced further by electron-donating R groups and arises from the large polarization of the C.-O bonds of the reactant radicals. The results suggest that the generation of alkyl radicals from ROC.=S should be particularly efficient when the R group bears radical-stabilizing and/or electron-accepting groups, such as CN. © 2006 American Chemical Society.