KINETICS OF REACTION OF HYDROGEN IODIDE WITH TETRAFLUORETHYLENE

The reaction between gaseous hydrogen iodide and tetrafluoroethylene is first order in both reactants between 176 and 222°. 1,1,2,2-Tetrafluoroethane and iodine are the major products and 1-iodo-1,1,2,2-tetrafluoroethane is the minor product. The presence of added iodine reverses the relative importance of the products but does not affect the rate constant. The activation energy for tetrafluoroethylene consumption is 20.5 ± 0.4 kcal/mol and A = 1.1 × 108 I./(mol sec). Unlike reactions between hydrogen iodide and alkenes, the principal rate-determining step is transfer of a hydrogen atom from hydrogen iodide to tetrafluoroethylene. The C-H bond dissociation energy of the CHF2CF2 radical is shown to be at least 49 kcal/mol, which is 10 kcal/mol greater than the corresponding bond energy of the ethyl radical.