Premium
New insight on an old reaction – the aqueous hydrolysis of acetic anhydride
Author(s) -
Wiseman Floyd Landis
Publication year - 2012
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.2945
Subject(s) - hydrolysis , chemistry , acetic anhydride , aqueous solution , catalysis , yield (engineering) , hydrolysis constant , organic chemistry , reaction mechanism , kinetics , reaction rate constant , thermodynamics , physics , quantum mechanics
Studies have shown that aqueous reactions generating a change in pH can be accurately monitored using a fast‐response pH electrode. This technique has been successfully applied in this work to the aqueous hydrolysis of acetic anhydride, which is a reaction that has been studied using a variety of techniques for nearly one hundred years. Many of these techniques involve elaborate equipment and sophisticated analyses, making the pH technique an attractive alternative. Studies here have focused on the temperature effects of the simple hydrolysis and acetate‐catalyzed hydrolysis reactions . Data analyses suggest the notion that if simple hydrolysis occurs by a two‐step mechanism, it does so only at low temperatures, whereas acetate‐catalyzed hydrolysis occurs almost assuredly by a single step mechanism. Results of this work yield the following values for the activation parameters for simple hydrolysis (subscripted with a “w”) and acetate‐catalyzed hydrolysis (subscripted with an “a”) at atmospheric pressure: Δ H w ‡ = 39.9 0.7 kJ ⋅ mol − 1 , Δ S w ‡ = − 227 ( 2 ) J ⋅ K − 1 ⋅ mol − 1 , Δ H a ‡ = 49.7 ( 0.3 ) kJ ⋅ mol − 1and Δ S ‡ a = − 157 1 J ⋅ K− 1⋅mol− 1. Implications of these results are discussed in this article. Copyright © 2012 John Wiley & Sons, Ltd.