A term used to characterize @R05066@ which have lifetimes of several minutes or greater in @D01739@ in @I03026@ solvents. Persistence is a kinetic or reactivity property. In contrast, radical @S05900@, which is a thermodynamic property, is expressed in terms of the C–H bond strength of the appropriate hydrocarbon. The @L03515@ of a radical is profoundly influenced by steric @S05644@ of the radical centre by bulky substituents.