A new procedure for the direct study of the chemical reactivity of peroxyl radicals (R-O-2(center dot)) is used. The particular TEA-O-2(center dot) radical (where TEA is the triethylamine moiety), directly observed by laser flash photolysis, is characterized by a strongly red shifted transition in the near visible wavelength range. This provides an original access to the interaction rate constants of TEA-O-2(center dot) with different additives (hydrogen donating compounds, electron acceptors, triphenylphosphine). Rate constants of hydrogen abstraction range from 1.9 x 10(2) to 1.1 x 10(6) M(-1)s(-1) for TEA-O-2(center dot) and roughly appear as governed in several systems by the reaction exothermicity. The interactions with triphenylphosphine are discussed. (C) 2007 Elsevier B.V. All rights reserved.