S1 Supporting Information for the article Extremely fast hydrogen atom transfer between nitroxides and HOO• radicals and implication in catalytic co-antioxidant systems Andrea Baschieri, a Luca Valgimigli,* a Simone Gabbanini, b Gino DiLabio, c,d Eduardo Romero- Montalvo, c Riccardo Amorati a * a) Department of Chemistry “G. Ciamician”, University of Bologna, Via S. Giacomo 11, 40126 Bologna, Italy. E-mail: Riccardo.amorati@unibo.it, Luca.valgimigli@unibo.it b) R&D division, BeC s.r.l., Via C. Monteverdi 49, 47122 Forli’, Italy. c) Department of Chemistry, University of British Columbia, 3247 University Way, Kelowna, British Columbia, Canada V1V 1V7 d) Faculty of Management, University of British Columbia, 1137 Alumni Ave, Kelowna, British Columbia, Canada V1V 1V7 Content pages Figure 1S-7s 2-6 Scheme 1S 6 Figures 8S-10S 7-8 Scheme 2S 9 Table 1 9 Figures 11S-15S 10-12 Figure 16S and Table 2S 13 Tables 3S-8S 14-15 Cartesian coordinates of optimized geometries 15-44