Two‐ and Three‐Dimensional Reactions of Ag+2 Radical Cations in Aqueous Solutions of Anionic Tensides

Abstract

AbstractAg+2 radical cations were produced in aqueous 1 · 10−4 molar Ag2SO4 solutions containing micelles of sodium hexadecyl trioxiethylene sulfate and of sodium dodecylsulfate by a short pulse of high energy electrons. The disappearance of Ag+2 and the appearance of Ag2 were followed by optical measurements in the 10−6 to 10−2 s range. – A fraction of the Ag+2 radicals decayed within 1 to 2 microseconds, and the remaining radicals disappeared in a second order process within 10−4 to 10−2 s. These decay processes are attributed to(a) intramicellar or two‐dimensional radical‐radical reaction at the surface of doubly occupied micelles, and(b) intramicellar or three‐dimensional reaction between radicals that are singly adsorbed at micelles. The fraction of (a) increases with increasing concentration ratio of radicals to micelles as expected from statistical considerations. Deviations at low concentration ratios are attributed to the initial formation of some of the radicals in spurs. The observed 100 fold acceleration of the radical‐radical reaction by the reduction in the dimensionality of reaction space is also compared to similar effects in fast biochemical reactions on large carrier molecules.It is concluded from an analysis of the dependence of the bimolecular rate constant of reaction (b) on the tenside concentration that Ag+2 cations reside longer than milliseconds at micelles and can be exchanged directly between two anionic micelles. The rate constants are given for the two tensides.