Interaction between trialkyl phosphites and aminoxyl radicals: a model study for polymer stabilization

2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) and its bis-1-oxyl analogue re act with triethyl and triisopropyl phosphite forming tetramethylpiperidine phosphite which is the main product of the reaction together with dialkyl p hosphates. Minor products are tetramethylpiperidinyldialkyl phosphate and t etramethylpiperidine. The reaction mechanism was elucidated by observing th e intermediate formation of the phosphoranyl radical which evolves forming the isolated products. The rate of this reaction is considerably lower comp ared to the stabilization reaction observed between phosphites and hydroper oxides during polymer oxidation. Thus the former reaction could be consider ed negligible in terms of polymer stabilization under the conditions studie d.