The stabilities of Meisenheimer complexes. Part III. Specific effects of cations in methanol solution

Abstract

The stoicheiometric equilibrium constants for the formation of Meisenheimer complexes from several substituted anisoles have been measured by use of dilute solutions of potassium, lithium, and tetra-n-butylammonium methoxides in methanol. The values obtained with potassium and tetra-n-butylammonium methoxide increase with increasing base concentration, an effect which is attributed to stabilisation of the complexes by association with the cations present. With lithium methoxide no such effect is observed and it is suggested that this base may be the most suitable for measurement of thermodynamic equilibrium constants.