PULSE-RADIOLYSIS STUDIES OF AMINOBENZENESULFONATES - FORMATION OF CATION RADICALS

Sulfanilic acid and anilinedisulfonic acids (ADS) react with OH radicals (k = 8.2 x 10(9) and 5.9 x 10(9) M-1 s-1) to form the corresponding OH adducts. In acid solutions the adducts react with protons to yield cation radicals (k = 5.3 x 10(8) and 8.7 x 10(8) M-1 s-1). N3 oxidizes sulfanilic acid directly to the cation radical by an electron-transfer reaction at a diffusion-controlled rate constant, k = 6.5 x 10(9) M-1 s-1, while the rate of oxidation of ADS by N3 is only 7.6 x 10(7) M-1 s-1. SO4- on the other hand oxidizes ADS to the cation radical at a rate of 1.8 x 10(9) M-1 s-1. Both cation radicals deprotonate to the anilino-type radicals in acid-base equilibria. The pK(a) of deprotonation of the sulfanilic cation radical is 5.8 +/- 0.05 and that of the ADS cation radical is 4.3 +/- 0.05.