A density functional study of dissociative electron transfer reactions with participation of halogenated methanes

Potential energy profiles characterizing the C–X bond cleavage in monohalomethanes CH3X (X = Cl, Br, I), polychlorinated methanes CHnCl4 − n (n = 0–3) and their anion radicals in water solutions were calculated using the density functional theory (DFT). In these calculations, solvent effects were accounted within the self-consistent reaction field (SCRF) model. The DFT potential energy curves were fitted by a Morse and an exponential function for the initial molecules and their breakdown products, respectively. The model functions were then employed to describe the kinetics of reductive cleavage of the C–X bonds in the halomethanes. The relevant calculations were carried out based on the non-adiabatic quantum-mechanical theory of dissociative electron transfer (DET). The values of the calculated rate constants correlate well with published experimental data and also with theoretical results previously obtained by the semi-empirical PM3 method.