| Popis: |
The adsorption and reactivity of radical ions on the macroreticular ion-exchange resin Amberlyst 15 have been studied using an ESR flow technique. Diffusion of N-methylphenothiazine (1) to Fe3+-labeled resin bead surfaces, with subsequent electron transfer to produce adsorbed 1•+, occurs about as quickly as the methanol eluant can penetrate into the interior of the resin matrix. In contrast, reactions of adsorbed 1•+ with reagents in the incoming eluant stream are slowed, and second-order reaction rates decrease on changing the reagent from ascorbic acid to diethylamine to cyclohexene. The degree of stabilization of adsorbed 1•+ appears to reflect the differing radical cation mobility requirements in these three reactions. The adsorption and reactivity of unsubstituted phenothiazine, thianthrene, and phenoxathin radical cations have also been investigated. The ESR technique used in these studies should be applicable to other paramagnetic systems as well, providing information on diffusion, adsorption, electron transfer reactions, and other reactions occurring within porous substrates. |
