This paper describes the application of LFER to understand the mechanism of the perhydrolysis of carboxylic acids over homogeneous and heterogeneous catalysts. Several experiments were carried out with different linear carboxylic acids: formic, acetic, propionic and butyric acids: using sulfuric acid and Amberlite IR-120 as catalyst and different reaction temperatures. From the experiments. the apparent I-ate constants decrease in the following order: k(app) (PFA) > k(app) (PAA) > k(app) (PPA) > k(app) (PBA), in both catalytic system. Furthermore it was found that this reaction follows Taft and Charton correlations, which implies that the steric effect of the substituent governs that reaction and the mechanism is similar between the different carboxylic acids. Comparison between homogeneous and heterogeneous catalytic system was carried out based oil the analysis of the kinetic expression. (C) 2009 Elsevier B.V. All rights reserved.