ACID-BASE BEHAVIOR IN SUPERCRITICAL WATER - BETA-NAPHTHOIC ACID AMMONIA EQUILIBRIUM

Equilibrium constants for the reaction of beta-naphthoic acid and ammo nia, K-BHA, were measured with UV-vis spectroscopy in water from 25 de grees C to 400 degrees C. At high density K-BHA decreases with tempera ture, the normal behavior for an exothermic reaction of a stronger aci d and base to a weaker acid and base. At low density, the reaction bec omes endothermic as the solvation of the ionic products becomes weaker . These data were combined with literature results for the dissociatio n of water and ammonia to determine equilibrium constants for the diss ociation of beta-naphthoic acid and the reaction of beta-naphthoic aci d and OH-. Whereas the density (and dielectric constant) of water have only a modest effect on the isocoulombic reaction of beta-naphthoic a cid and OH-, they have a large effect on all of the other reactions wh ich are ionogenic.