Hammett acidity functions (H–) of lithium, sodium, and potassium glycoxide solutions in ethylene glycol at 25 °C

Abstract

H _– scales have been set up for solutions of lithium, sodium, and potassium glycoxides in anhydrous ethylene glycol at 25 °C by use of nitro-substituted anilines and diphenylamines as indicators. The order of increase of H_– with alkali concentration is Li < Na < K. This may be due to ion-pair formation which will be in the order Li > Na > K, and is reflected in the H_– being in the reverse order, as expected. The H_– scales for the three systems (i) NaOH in water, (ii) NaOMe in methanol, and (iii) Na glycoxide in ethylene glycol are compared. A comparison is also made of the aqueous and glycolic systems on a mole-fraction scale, which seems to indicate that, like the autoprotolysis constant, the H_– scale in any amphiprotic solvent is largely a composite function of bulk dielectric constant of the solvent, as well as the intrinsic acidity and basicity of the solvent molecules.