Electrochemically Induced SRN1 Aromatic Nucleophilic Substitution. Absolute Reactivities of Phenyl Derivatives in Liquid Ammonia

Article abstract of DOI:10.1021/ja00303a007

Homogeneous redox catalysis of the electrochemical reductive cleavage of diphenyl sulfide is used for determining the absolute reactivity of phenyl radicals toward benzenethiolate and diethyl phosphite ions in liquid ammonia.Other redox catalysis data obtained with chlorobenzene as the substrate as well as the direct electrochemistry of the two substrates appear to be consistent with these determinations.The cleavage rate constants of the anion radicals of PhSPh and PhCl and the standard potentials of the corresponding redox couples were also determined.Phenyl radicals appear to be significantly less reactive than most of the other aryl radicals, giving rise to nucleophilic attack rate constants that are well below the diffusion limit.PhS(1-) is shown to be markedly less reactive toward phenyl radicals than the other usual S_RN1 nucleophiles.The observed reactivities are discussed in terms of transfer of the unpaired electron from the ?^* carbon-nucleophile bond orbital to the ?^* orbital of the aromatic ring during the addition reaction.