Abstract: The unusual occurrence of simultaneous electrophilic (two-electron) and electron- transfer (one-electron) pathways during the thallation of the homologous methylbenzenes ArCH3 is demonstrated by (1) the careful analysis and identification of three major types of products,(2) the complete dissection of the complex kinetics, and (3) the identification of the reactive intermediates by time-resolved UV-vis and ESR spectroscopy. Side-chain ...