Abstract
In this communication we present the results of an EPR and electrochemical investigation on free radicals produced by electrochemical reduction, at controlled potential, of the following alkyl substituted perfluoro-olefins: R 1R 2CCR 3R 4 1. R 1R 2R 3R 4Me 2. R 1R 3Me, R 2R 4Et 3. R 1R 2i-Prop, R 3Me, R 4F 4. R 1R 2Me, R 3i-Prop, R 4Et All the olefins studied present, in acetonitrile, a chemically reversible one-electron reduction step in the range 0.4–0.8 V vs. Ag/AgCl, corresponding to the formation of the radical anion. The latter is some cases can be accumulated by macroscale electrolysis at low temperature (0 to −30 °C). At more negative potentials, the radical anions are reduced to the corresponding dianions, which are very unstable because of a fast fragmentation process. The EPR spectra are characterized by very large hyperfine coupling constants of the unpaired electron with 19F nuclei directly bonded to the unsaturated carbon atom, with the β 19F nuclei of the alkyl groups and additional couplings to γ 19F nuclei, indicating a significant contribution of the fluorine orbitals to the molecular orbital occupied by the unpaired electron. The spectra show a strong dependence on the temperature which is fully described by a restricted rotation of the perfluoro-alkyl groups, including perfluoro-methyls, about the single bonds.
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