RATE-CONSTANT OF CARBON HALOGEN DISSOCIATIVE REDUCTION IN HALOALKANES- EVALUATION OF COMPUTATIONAL MODELS

Models describing kinetics of dissociative reduction of haloalkanes ar e quantitatively compared at various values of constiuent parameters o f the U(f) potential, which characterizes the carbon-halogen bond in c orresponding radical anions. For sufficiently steep potentials U(f), h armonic approximation leads to a significant error as compared with th e formula based on the Morse function. The reaction rate constant is s trongly dependent on constituent parameters B and beta of the U(f) pot ential. At large negative values of the reaction free energy, the quan tum mechanical model involves the tunnelling transition the from lower vibrational levels of the haloalkane-molecule C-X bond. Replacement o f common carbon with its isotope significantly affects the process.