Effects of or on the Reaction Rates

Effects of the inert inorganic salts on the rate constants (k) for the reactions involving ionic reactants are generally explained in terms of the Debye-Huckel or extended Debye-Huckel theory. In actuality, the extended Debye-Huckel theory involves an empirical term, which makes the theory a semiempirical theory. However, there are many reports in which the effects of salts on k of such ionic reactions cannot be explained by the Debye-Huckel theory. For instance, pseudo-first-order rate constants (k bs) for the reaction of HO with acetyl salicylate ion (aspirin anion) show a fast increase at low salt concentration followed by a slow increase at high concentration of several salts. But the lowest salt concentration for each salt remains much higher than the limiting concentration (0.01 M for salts such as M+X ) above which the Debye-Huckel theory is no longer valid. These k bs values fit reasonably well to Equation 7.48 

Rate-decreasing effects of the concentration of caffeine and theophylline-7-acetate (the additives) have been observed for the alkahne hydrolysis phenyl and substituted phenyl benzoates.  

Pseudo-first-order rate constants for the alkaline hydrolysis of these esters in the presence of a series of varying concentrations of caffeine and theophylline-7-acetate obey Equation 7.48 with [M XJ replaced by [caffeine] or [theophylline-7-acetate]. 

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