Abstract
The addition reactions of CH3, CH2F, CHF2 and CF3 radicals to ethylene, monofluoroethylene, difluoroethylene, trifluoroethylene and tetrafluoroethylene have been investigated by using density functional theory (DFT) and Hartree-Fock (HF) methods. In the DFT calculations we have used both pure and hybrid (partly including HF) exchange and Lee/Yang/Parr or Perdew/Wang 91 correlation functionals with the 6-31 G* basis set. The same basis was taken in the HF calculations. For all possible combinations of fluorosubstituted methyl radicals and ethylenes, the structures of reactants and transition states have been located. Inclusion of electron correlation was shown important in reproducing experimental activation barriers. In addition, the results were strongly dependent on the type of functionals. The Becke's three-parameter hybrid with Perdew/Wang 91 gradient-corrected correlation functional B3PW91 gave the best estimates of the activation energies.
