Absolute rates of intermolecular carbon-hydrogen abstraction reactions by fluorinated radicals

Using competition kinetic methodology, absolute rate constants for bimolecu lar hydrogen abstraction from a variety of organic substrates in solution h ave been obtained for the n-C4H9CF2CF2., n-C4F9., and i-C3F7. radicals. Flu orine substitution substantially increases the reactivity of alkyl radicals with respect to C-H abstraction, with the secondary radical being most rea ctive. A wide range of substrate reactivities (5200-fold) was observed, wit h the results being discussed in terms of an interplay of thermodynamic, po lar, steric, stereoelectronic, and electrostatic/field effects on the vario us C-H abstraction transition states. Representative carbon-hydrogen bond d issociation energies of a number of ethers and alcohols have been calculate d using DFT methodology.