Hydrolysis of ethyl isovalerate in aqueous hydrochloric and sulfuric acid solutions

Abstract

1. Effective rate constants (kef) for the hydrolysis of ethyl isovalerate in aqueous solutions containing from 4.95 to 41.3 mass % HCl, or from 2.52 to 94.0 mass % H2SO4, have been determined spectrophotometrically at 25°C. 2. The quantity kef increases with increasing acid concentration in aqueous HCl solutions. In aqueous sulfuric acid solutions, kef passes through a maximum at 49.8–55.9% H2SO4 and a minimum at 74.9% H2SO4. 3. In the hydrochloric acid and sulfuric acid solutions in question here (up to 74.9% H2SO4), the hydrolysis of ethyl isovalerate proceeds through an activated complex containing one un-ionized ester molecule and one hydronium ion carrying at least one solvation water molecule. The water molecule functions here as a nucleophilic agent. 4. The data obtained can be interpreted quantitatively by assuming that ionizatioa results in the formation of a protonized form of the ester and an unreactive complex in which the carbonyl group oxygen is bound to the hydronium ion. 5. Hydrolysis proceeds through the protonized form of the ester in sulfuric acid solutions with concentrations in excess of 74.9%.