Reactivity of fluorocarbon radicals in the low-temperature fluorination ofunsaturated perfluorocarbons

Calorimetry and ESR spectroscopy were used to study the low-temperature flu orination (77-300 K) of unsaturated perfluorocarbons with fluorine. In the solid phase at 77-100 K (glassy or crystalline state) fluorination does not occur. On transition from glassy systems to the supercooled liquid state f ormation of molecular complexes in which fluorine is attached to the \raste r="rg102">C=C\raster="rg101" bond becomes possible. These complexes are sta bilized on crystallization of the system; with a further increase in temper ature, efficient addition of molecular fluorine takes place in the crystal phase. However, the addition of fluorine by a chain or carbene mechanism mu st not be ruled out for such systems. Thus, in the case of hexafluoropropen e trimer, the addition proceeds as a chain reaction producing long-living f oe radicals at the initial stage. (C) 1999 Elsevier Science S.A. All rights reserved.