A study was carried out on the solvolysis of the following substituted benzoyl chlorides in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane/water microemulsions: 4-CH3O, 3,4-(CH3O)(2), 4-CH3, 4-H, 4-Cl, 3-Cl, 4-CF3, 3-CF3, 3-NO2, and 4-NO2. The benzoyl chlorides are found distributed between the isooctane and the interface, where they react with its hydration water. From the kinetic data we have been able to obtain the true rate constant for the reaction at the interface, k(i). Two extreme types of behavior have been observed: for those processes which occur via a predominantly dissociative pathway, k(i) decreases together with W (W [H2O]/[AOT]), while for those processes which occur through a predominantly associative pathway, the rate constant at the interface, k(i), increases as W decreases. The decrease of k(i) with W is interpreted as being due to the capacity of interfacial water for solvating the leaving Cl-. For the associative process, the increase in the nucleophilic capacity of the interfacial water as W decreases is the factor responsible for the increase in k(i), so that the lesser capacity for solvation of the transition state can be compensated for as the water content of the microemulsion decreases. A comparative analysis of the reactivity of substituted benzoyl chlorides at the interface of the microemulsion shows an increase of the rate of the associative pathway and a decrease of the dissociative counterpart. Hence for W = 50, the change between the two reaction pathways is observed for the benzoyl chlorides with substituents 4-Cl and 3-Cl, while in bulk water this change takes place with more electron-attracting substituents. When the water content of the microemulsion decreases (W = 2), only the benzoyl chlorides 4-CH3O and 3,3-(CH3O)(2) will react predominantly through the dissociative pathway.