PROTON MAGNETIC RESONANCE STUDY OF WATER-AMMONIA PROTON EXCHANGE IN WATER-AMMONIA SOLUTIONS CONTAINING ADDED POTASSIUM HYDROXIDE

The exchange of protons between H2O and NH3 in solutions of H2O in liquid NH3 at 29.6 ± 0.2° is accelerated by addition of OH-. The overall kinetics for H2O concentrations from 1 to 12 M and added [OH-] from zero to ∼ 2 × 10-3 M is well represented by rate = k1[OH-] + k2[OH-][H2O]2 + k3[NH4+][H2O] + k4[H2O]4 with k1 = 7.4 × 104 sec-1, k2 = 0.84 × 104 sec-1 M-2, k3 = 3.48 × 106 sec-1 M-1, and k4 = 0.058 sec-1 M-3. At the highest H2O concentrations, the effect of the third term in the above rate expression allows one to place rather narrow limits on the ionization of H2O in liquid NH3. Thus at 12.2 M H2O, kion = [NH4+][OH-]/ [H2O] = (3.9 ± 0.3) × 10-11 and at 9.05 M H2O, Kion = (1.1 ± 0.1) × 10-11. The remaining terms in the rate expression suggest possible species in these systems.