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

Abstract

2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) and its bis-1-oxyl analogue react with triethyl and triisopropyl phosphite forming tetramethylpiperidine phosphite which is the main product of the reaction together with dialkyl phosphates. Minor products are tetramethylpiperidinyldialkyl phosphate and tetramethylpiperidine. The reaction mechanism was elucidated by observing the intermediate formation of the phosphoranyl radical which evolves forming the isolated products. The rate of this reaction is considerably lower compared to the stabilization reaction observed between phosphites and hydroperoxides during polymer oxidation. Thus the former reaction could be considered negligible in terms of polymer stabilization under the conditions studied.