Secondary radical formation and electron spin polarization in systems involving phosphonyl radicals

Abstract

Addition of electron spin polarized primary phosphonyl radicals to carbon–carbon double bonds yields secondary radicals the chemical identity of which is obtained from the analysis of the hyperfine structure of their ESR spectra. These radicals exhibit spin polarization (CIDEP) characteristic of a polarization transfer process. The CIDEP patterns reveal the relative signs of the hyperfine couplings in the primary and secondary species. The spectra also exhibit the effects of hyperfine-dependent relaxation unusually clearly, from which the relative signs of the couplings may, in principle, be obtained in these secondary radicals also. Further reaction of the secondary radical to form a tertiary one sometimes also occurs, again with polarization transfer. An example is given of an instance in which a difference in the signs of the coupling constants in these two species leads to a phase reversal in the spectrum of the polarized tertiary radical as a result of this process.