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.