Acetal formation from methyl formate, pinacolone, and benzophenone: equilibrium constants in methanol and water determined by a chain of transacetalization equilibria

Abstract

Transacetalization equilibrium constants can be measured in methanol solution. This allows a ladder of equilibrium constants to be constructed from acetophenone, for which the equilibrium constant for acetal formation has been measured in methanol, to methyl formate, for which it has not. This is the first direct measurement of an equilibrium constant for formation of an acetal of an acyclic ester. We have also determined equilibrium constants for acetal formation from benzophenone and pinacolone. The value for benzophenone is inconsistent with the value reported for the diethyl acetal by Pfeiffer and Adkins (G.J. Pfeiffer and H. Adkins. J. Am Chem. Soc. 53, 1043 (1931)). We must conclude that their analytical method was subject to systematic errors.