Comparative DFT study of non-fluorinated and perfluorinated alkyl and alkyl-peroxy radicals

Thermodynamic properties of small alkyl and alkyl-peroxy radicals are studied to model primary, secondary and tertiary radicals in non-fluorinated and perfluorinated polymers. Bond strengths, bond lengths, and total atomic charges from the Mulliken population analysis are calculated using the B3LYP DFT method with spin-restricted orbitals. On this basis we find that the experimentally observed conversion of alkyl-peroxy to alkyl radicals is most likely by detachment of molecular oxygen or possibly by hydrogen but not by fluorine abstraction, although all of these reactions are predicted to be endothermic. Fluorine substitution leads to interesting charge polarization effects.