Pulse radiolysis and polarography: influence of the double layer capacity on electrode reactions of short-lived radicals in aqueos solutions

Abstract The polarograms of free radicals measured in the 10 −5 s range often show distortions caused by strong changes in the differential capacity of the double layer. This effect is discussed for the radicals produced by OH attack on benzene, benzyl alcohol and t‐butanol. The observation of these distortions leads to the conclusion that the relaxation of the double layer is very fast, i.e. occurs within a time shorter than a few microseconds. The time dependence of polarographic currents in the 10 −5 s range can be influenced by two effects at the Hg drop electrode: The action of the double layer as an "electrical condenser" for ion pairs produced in electrode processes with high transfer rates, and the action of mercury as an "adsorption condenser" that stores free radicals by chemisorption at low transfer rates. A few observations on the catalysis of the cathodic reaction of the t‐butanol radical, .CH 2 C(CH 3 ) 2 OH, by H + ions are also reported. A mechanism is proposed where the reduction of the protonated radical is accompanied by rapid elimination of water yielding isobutene.