The reactions of hydrated electron (e(aq)(-)) with various radicals have been studied in pulse radiolysis experiments. These radicals are hydroxyl radical ((OH)-O-center dot), sulfite radical anion ((SO3-)-S-center dot), carbonate radical anion (CO3 center dot-), carbon dioxide radical anion ((CO2-)-C-center dot), azidyl radical (N-center dot(3)), dibromine radical anion (Br-2(center dot-)), diiodine radical anion (I-2(center dot-)), 2-hydroxy-2-propyl radical (C-center dot(CH3)(2)OH), 2-hydroxy-2-methyl-1-propyl radical (((CH2)-C-center dot)(CH3)(2)COH), hydroxycyclohexadienyl radical ((C6H6OH)-C-center dot), phenoxyl radical (C6H5O center dot), p-methylphenoxyl radical (p-(H3C)C6H4O center dot), p-benzosemiquinone radical anion (p-OC6H4O center dot-), and phenylthiyl radical (C6H5S center dot). The kinetics of e(aq)(-) was followed in the presence of the counter radicals in transient optical absorption measurements. The rate constants of the e(aq)(-) reactions with radicals have been determined over a temperature range of 5-75 degrees C from the kinetic analysis of systems of multiple second-order reactions. The observed high rate constants for all the e(aq)(-) + radical reactions have been analyzed with the Smoluchowski equation. This analysis suggests that many of the e(aq)(-) + radical reactions are diffusion-controlled with a spin factor of (1)/(4), while other reactions with (OH)-O-center dot, N-center dot(3), Br-2(center dot-), I-2(center dot-), and C6H5S center dot have spin factors significantly larger than (1)/(4). Spin dynamics for the e(aq)(-)/radical pairs is discussed to explain the different spin factors. The reactions with (OH)-O-center dot, N-center dot(3), Br-2(center dot-), and I-2(center dot-) have also been found to have apparent activation energies less than that for diffusion control, and it is suggested that the spin factors for these reactions decrease with increasing temperature. Such a decrease in spin factor may reflect a changing competition between spin relaxation/conversion and diffusive escape from the radical pairs.