Pulse Radiolysis Studies of Aminobenzenesulfonates: Formation of Cation Radicals

Article abstract of DOI:10.1021/j100172a078

Sulfanilic acid and anilinedisulfonic acids (ADS) react with OH radicals (k = 8.2 * 10⁹ and 5.9 * 10⁹ 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 * 10⁸ and 8.7 * 10⁸ 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 * 10⁹ M^-1 s^-1, while the rate of oxidation of ADS by N3 is only 7.6 * 10⁷ M^-1 s^-1.SO4^- on the other hand oxidizes ADS to the cation radicalat a rate of 1.8 * 10⁹ 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.