Determination of Steric Effect on the Esterification of Different Alcohols with Propanoic Acid over Cation-exchange Resin Catalyst Dowex 50Wx4

摘要

This paper describes the application of LFER in the form of Taft correlation to understand the mechanism of the esterification of propanoic acid with different alcohols over heterogeneous catalyst, Dowex 50Wx4. The rate constant (k1) in the rate equation decreases with change of alcohols in the order methanol, ethanol, n-propyl, n-butyl, n-pentyl, iso-butyl, iso-propyl and sec-butyl (2-buthanol). The reaction of propanoic acid with alcohols fits the Taft equation, log k1/k_(CH3) = 1.0061 E_s — 0.0012, which implies that the steric effect of the substituent governs that reaction and the mechanism is similar between the different alcohols. The experimental results were modelled according to a simple second-order model. It was found that the equilibrium constant of this reaction does not depend on the structure of the organic alcohols, and has for 333 K the value 4.04.