AbstractThe kinetics of the homolytic substitution of several trialkyltin iodides by iodine atoms are presented. Rate constants have been determined at three different temperatures and the following activation parameters calculated:A,Ea, and ΔS°≠. The observation that the activation energy, ΔG≠, is related to the driving force of the ion‐pair formation, leads to the conclusion that the charge‐transfer model is a valid approach for substitution in the reaction between R3SnI compounds and io