DISSOCIATION-CONSTANTS OF ACETIC, PROPIONIC, AND N-BUTYRIC ACIDS IN 25-MASS AND 50-MASS PERCENT 2-PROPANOL + WATER FROM 10-DEGREES TO 25-DEGREES-C

Electromotive-force measurement of cells with hydrogen gas electrodes and silver-silver chloride electrodes have been used to determine the pK values of acetic acid, propionic acid, and n-butyric acid in 25 and 50 mass % 2-propanol + water at eight temperatures from -10 to 25 °C. Hydrogen gas electrodes and silver chloride electrodes were used, and the cell was free from liquid junctions. The data were used to derive the standard changes of Gibbs energy, enthalpy, and entropy for the dissociation processes. A comparison with data for the water solvent shows that addition of 2-propanol to the solvent medium increases pK and the Gibbs energy change for each of the acids, while the entropy of dissociation becomes increasingly negative. © 1990, American Chemical Society. All rights reserved.