Mechanistic aspects of beta-bond-cleavage reactions of aromatic radical cations

The mesolytic cleavage of a beta-C-X bond (ArCR2-X.+ --> ArCR2./+ + X+/.) i s one of the most important reactions of alkylaromatic radical cations. In this Account, our group's results concerning some fundamental aspects of th is process (cleavage mode, structural and stereoelectronic effects, competi tive breaking of different beta-bonds, nucleophilic assistance, possible st ereochemistry, carbon vs oxygen acidity in arylalkanol radical cations) are presented and critically discussed for reactions where X = H, CR3, SR, and SiR3. Several examples illustrating how this information was exploited as a tool to detect electron-transfer mechanisms in chemical and enzymatic oxi dations are also reported.