Exchange of organic radicals between solution and organo-cobalt complexes is experimentally observed and the reaction pathway is probed through DFT calculations. Cyanoisopropyl radicals from AIBN (2,2'-azobisisobutyronitrile) enter solutions of cobalt(II) tetramesityl porphyrin ((TMP)Co-II center dot, 1) and vinyl acetate (VAc) in benzene and react to produce transient hydride (TMP)Co-H and radicals (center dot CH(OAc)CH2C(CH3)(2)CN (R-1 center dot)) that proceed on to form organo-cobalt complexes (TMP)Co-CH(OAc)CH3 (4, Co-R-2) and (TMP)Co-CH(OAc)CH2C(CH3)(2)CN (3, Co-R-1), respectively. Rate constants for cyanoisopropyl radical addition with vinyl acetate and hydrogen atom transfer to (TMP)Co-II center dot are reported through kinetic studies for the formation and transformation of organo-cobalt species in this system. Rate constants for near-degenerate exchanges of radicals in solution with organo-cobalt complexes are deduced from H-1 NMR studies and kinetic modeling. DFT computations revealed formation of an unsymmetrical adduct of (TMP)Co-CH(OAc)CH3 (4) with center dot CH(OAc)CH3 (R-2 center dot) and support an associative pathway for radical interchange through a three-centered three-electron transition state [R center dot center dot center dot Co center dot center dot center dot R]. Associative radical interchange of the latent radical groups in organo-cobalt porphyrin complexes with freely, diffusing radicals in solution that is observed in this system provides a pathway for mediation of living radical polymerization of vinyl acetate.