Determination of relative acidity scales for some dipolar aprotic solvents by coulometry using a hydrogen-palladium electrode

A coulometric-potentiometric procedure for the determination of relative acidity scales of acetone, methylethyl ketone, methyl-isobutyl ketone and propylene carbonate is described. The range of the relative acidity scale of a solvent was determined from the difference between the half-neutralization potential of perchloric acid and that of tetrabutylammonium hydroxide. The perchloric acid was generated in situ from a hydrogen-palladium electrode in presence of sodium perchlorate or tetrabutyammonium perchlorate as the supporting electrolyte. The electrode pairs glass-SCE and (H-2/Pd)(ind)-SCE were applied for the measurement of the half-neutralization potentials of the acid and base. A wider range of relative acidity scale of the solvents was obtained with the glass-SCE electrode pair and tetrabutylammonium perchlorate as the supporting electrolyte.