Pulse Radiolysis Studies. XVII. Reaction Kinetics of Molecular Cations of Aromatic Compounds in Dichloroethane Solution

Fast reaction studies of the kinetics of molecular cations of aromatic molecules, formed by irradiation of the aromatic compounds in 1,2-dichloroethane solution, have provided quantitative information about the modes of formation and of decay of these molecule ions. Specific reaction rates have been determined for the electron transfer from a neutral aromatic molecule to an aromatic cation for three donor–acceptor pairs. The rate of formation of the aromatic cation, thought to be a charge transfer from the aromatic molecule to the solvent cation, is so high as to suggest that migration of the solvent cation is not a process of molecular diffusion, but involves an electron jump process in the solvent. The decay of the aromatic cation appears to be due largely to recombination with the counterion. Absolute rate constants for electron transfer between the aromatic pairs studied are at or near diffusion controlled, with values ranging from 5.1 × 109 to 9.9 × 109M−1·sec−1 at 25°C.