Detection of 4-iodo-2,2-dimethyloctanenitrile and 2-iodo-2-methylpropanenitrile proved an operation of two types (I and II) of initiation in the I-ATRA reaction. 4-Iodo-2,2-dimethyloctanenitrile, resulting from the isobutyronitrile radical attack onto 1-hexene followed by the iodine atom transfer (type II), was formed in reactions of EWG-CH(R)-I [R = H, Me; EWG = (EtO) 2 P(O), (-)-(MenthylO) 2 P(O), CN, Br-C 6 H 4 C(O), MeO(O)C, allyl] with 1-hexene. Nitriles of analogous structures were also detected in reactions of (EtO) 2 P(O)CH(R)-I with 1-heptene, 1heptyne, cyclopentene, cyclohexene, and propargyl alcohol. 2-Iodo-2-methylpropanenitrile as the product of the isobutyronitrile attack onto iodine atom of the starting iodide was detected for the first time in the reaction of allyl iodide and 1-hexene and proved an operation of the cooperating pathway of initiation (type I)
. EPR experiments, performed directly in the spectrometer cavity, confirmed extremely low concentration of reacting radical species (for a sample of c = 0.1 mol/dm 3 , <10 -8 mol/dm 3 , or <10 -12 moles of spins in a sample) in I-ATRA reactions involving low reactive 1-iodoalkylphosphonates.