Switchover of reactions of solvated electrons with nitrate ions and ammonium ions in propanol–water solvents

Abstract

The reaction rate constants of [Formula: see text] with ammonium nitrate (~ 0.1 mol m−3) in 1-propanol-water and 2-propanol–water binary solvents correspond to [Formula: see text] reaction in the water-rich solvents, and to [Formula: see text] reaction in alcohol-rich solvents. The overall rate constant is smaller in solvents with 40–99 mol% water, with a minimum at 70 mol% water. The Arrhenius temperature coefficient is 26 kJ mol−1 in each pure propanol solvent, increases to 29 kJ mol−1 at 40 mol% water, then decreases to 17 kJ mol−1 in pure water solvent. The high reaction rates in the single component solvents, alcohol or water, are limited mainly by solvent processes related to shear viscosity (diffusion) and dielectric relaxation (dipole reorientation). Rate constants reported for concentrated solutions (50–1000 mol m−3) of ammonium and nitrate salts in methanol (Duplâtre and Jonah. J. Phys. Chem. 95, 897 (1991)) have been quantitatively reinterpreted in terms of the ion atmosphere model.