ABNORMAL SALT EFFECTS ON A CATION/ANION REACTION. AN INTERPRETATION BASED ON THE ANALYSIS OF THE COMPONENTS OF THE EXPERIMENTAL RATE CONSTANT

摘要

Salt effects (NaNO3) on the kinetics of the reactions [Fe(CN)6]~(3-) + [Ru(NH3)5(pyz)]~(2+) = [Fe(CN)6]~(4-) + [Ru(NH3)5(pyz)]~(3+) (pyz = pyrazine) were studied through T-jump measurements. An abnormal (positive) salt effect on the forward reaction was observed and a normal (negative) effect on the reverse one. These facts imply an asymmetric behavior of anion/cation reactions depending on the charge sign of the oxidant and reductant. The results can be rationalized by using the Marcus-Hush treatment for electron-transfer reactions after decomposition of the experimental rate constants into their components.