MEASUREMENT OF RATE PROCESSES OF FREE RADICALS IN HOMOGENEOUS AND MICELLAR SOLUTIONS BY CIDNP

Article abstract of DOI:10.1016/S0040-4020(01)92390-7

CIDNP is used to study rate processes of free radicals in both homogeneous and micellar solutions.An estimate of the lifetime of the phenyl-acetyl radical at ambient temperature (τ_-CO>/=1E-7sec) produced during photolysis of dibenzyl ketone is made based on quantitative CIDNP measurements and computer simulations.Observation of CIDNP in micellar solution is shown to be consistent with an isotropic medium which restricts diffusion on a short time scale, allowing for an increased tendency toward cage reaction.In the case of t-butyl/pivaloyl radical pairs, escape of the radical fragments from the micelle is shown to be competitive with decarbonylation of the pivaloyl radical.Likewise, CIDNP is consistent with product yield results which show the enhanced tendency of triplet born benzyl radical pairs to undergo cage reaction when they are sequestered in a micelle.