RADICAL REACTION-KINETICS DURING HOMOLYSIS OF N-ALKOXYAMINES - VERIFICATION OF THE PERSISTENT RADICAL EFFECT

N-Alkoxyamines cleave into transient alkyl and persistent aminoxyl rad icals which then combine and regenerate the parent compounds. Simultan eously, the alkyl species self-terminate, and this causes a continuous build-up of excess aminoxyl. Hence, the back-reaction to the alkoxyam ine accelerates and the self-termination slows down in time. An analys is of this self-regulating Persistent Radical Effect shows that in the absence of scavengers the alkoxyamines decay and the aminoxyls appear according to unusual t(1/3) rate laws governed by a rate constant com bination. This is verified by studying the aminoxyl release from (2',2 ',6',6'-tetramethylpiperidine-1'-oxyl)propane (cumyl-TEMPO). The rate constants of the individual reactions are also determined under isolat ion conditions and explain the behaviour of the combined reaction syst em. Mechanistic details of the reactions are given, and their relevanc e for 'living' radical polymerizations is pointed out.