Density functional theory calculations of the effect of fluorine substitution on the cyclobutylcarbinyl to 4-pentenyl radical rearrangement

The effects of fluorine substitution on the cyclobutylcarbinyl to 4-pentenyl radical rearrangement and on the strain of cyclobutane have being studied using density functional theory, the ring-opening being modestly inhibited and the strain generally not greatly affected. Perfluorocyclobutane is predicted to have 6 kcal/mol less strain than cyclobutane. Cyclizations of 1,1,2,2-tetrafluoro- and 1,1,2,2,3,3-hexafluoro-4-pentenyl radicals should be significantly enhanced (similar to 2400 times faster) relative to the parent system. The calculations are consistent with the few experimental data available.