PRIMARY SALT EFFECT ON RATE OF REACTION BETWEEN LIKELY CHARGED IONIC SPECIES BY POLYELECTROLYTES

The rate constants were measured in the presence of various polyelectrolytes for the following two types of reactions between likely charged ionic species, namely bromoacetate-thiosulfate ion reaction and bromopentaamminecobaltic ion-mercuric ion reaction. Cationic polyelectrolytes such as polyethylenimine hydrochloride considerably enhanced the anion-anion reaction, whereas polystyrenesulfonate and other anionic polyelectrolytes also showed large accelerating effects on the cation-cation reaction. This primary salt effect by polyelectrolytes was markedly larger than that by simple electrolytes and was shown to be due to a lowering of the enthalpy and entropy of activation in contrast to the simple electrolyte cases in which these thermodynamic quantities were increased. The entropy loss by the addition of polyelectrolytes was in conformity to the enhanced regularity of ionic distribution in the polyelectrolyte solutions, which was previously concluded from the mean activity coefficient measurements. © 1968, American Chemical Society. All rights reserved.