Degradation mechanisms of peroxide-containing compounds, either stable or transients in the degradation of volatile organic compounds, are still poorly understood, despite their importance in atmospheric chemistry. A theoretical DFT and Coupled Cluster theory analysis of the stability of alkyl radicals with hydroperoxyl- (HOO-) or alkylperoxyl (ROO-) substituents on the radical carbon atom revealed that such radicals are unstable, dissociating by O-O scission to a carbonyl compound and a hydroxy or alkoxy radical even for multiple substituted compounds. This dissociation occurs sequentially after completion of the reaction forming the a-peroxyl-substituted radicals, such that the latter is independent of the O-O scission. (C) 2004 Elsevier B.V. All rights reserved.