On the Interpretation of Reaction Rates in Concentrated Acid Solutions

Abstract

The model of Bascombe and Bell for the indicator acidity of concentrated acid solutions is applied to the analysis of acid catalyzed reactions. A number of well studied reactions are shown to obey the relationship: where Cw is the molar concentration of water not bound to proton (or to hydroxyl OH−). Values of Cw for use in the above correlation are calculated, assuming the existence of the proton in the form suggested by Eigen, H3O(H2 O)3+. The volume fractions of nonbound water are also calculated, this quantity giving even better correlation in some cases. Values of n are obtained which agree, after subtraction of water molecules given up by the proton, with the number of water molecules which can be expected to participate in the formation of the transition state of these reactions.

Hydration Numbers of Some Acids and Salts

“…Bascombe and Bell [ 1 ] have suggested that this behavior may be caused by the decrease in water solvent concentration due to hydration of the proton with four molecules of water [2]. The subject has been reviewed recently [3,4]. The same argument can be applied to determine the hydration number of salts.…”