ABSTRACT Recent investigations of solvent effects on the rate constants for reactions described as the intramolecular electron transfer (or electron shift) concerted in one-step with bond interchange (i.e. bond breaking and/or making) are analyzed. Theoretical models of Savéant and Marcus for kinetics of such reactions are briefly reviewed. They predict two solvent dependent contributions to the activation barrier: one related to the thermodynamic driving force and the other to the intrinsic barrier, mainly originated from non-equilibrium solvent polarization. Both solvent effects are analyzed for kinetics of bond cleavage in aromatic radical anions containing halogen atoms as leaving groups and for simple SN2 Finkelstein reactions between methyl iodide and anionic nucleophiles. The importance of the effect of non-equilibrium solvent polarization is supported by dependencies of the intrinsic activation barrier, obtained in different solvents, on the solvent Pekar factor. Solvent effect on the rate constants for protonation of radical anions of anthracene, forming -CH acids, is also discussed in terms of the recently proposed mechanism of concerted electron and hydrogen atom transfer.
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