Self-recombination rate constants for 2-propanol and tert-butyl alcohol radicals in water

The techniques of electron pulse radiolysis and direct detection ESR have b een used to determine Arrhenius parameters for the self-recombination of 2- propanol (hydroxymethylethyl) and tert-butyl alcohol (2-hydroxy-2,2-dimethy l-propyl) radicals in water. Rate constants of 2k(7) = (1.56 +/- 0.10) x 10 (9) and 2k(23) = (1.18 +/- 0.20) x 10(9) dm(3) mol-(1) s-(1) for these radi cals were measured at 26.4 and 26.6 degrees C, respectively, with correspon ding activation energies of 18.8 +/- 1.2 (5.3-71.7 degrees C) and 15.83 +/- 0.92 (8.5-69.8 degrees C) kJ mol(-1) for these two reactions. These data a re compared to available literature rate constants, and also to the results of diffusion-controlled rate constant calculations, which demonstrate that radical reactivity, not diffusion, dominates both recombination processes in water.