KINETICS AND MECHANISM OF THE REACTION OF (NH2)-N-CENTER-DOT WITH O-2IN AQUEOUS-SOLUTIONS

The reaction of NH3 With (OH)-O-. or SO4.- radicals produces the aminy l radical, (NH2)-N-.. Pulse radiolysis and laser flash photolysis tech niques were utilized to study the formation of this radical, its absor ption spectrum, its reaction with O-2, and the mechanism of formation of subsequent intermediates and the main final product, peroxynitrite. The rates of formation of (NH2)-N-. and its absorption spectrum are i n agreement with previous reports. The reaction of (NH2)-N-. with O-2, however, was observed to take place much more rapidly than reported b efore and to involve an equilibrium of these reactants with the aminyl peroxyl radical, NH2O2.. The equilibrium is shifted toward completion of the reaction via catalyzed decomposition of this peroxyl radical, a nd this decomposition affects the observed rate of reaction of (NH2)-N -. with O-2. The peroxyl radical deprotonates and isomerizes and final ly forms NO. In the presence of O-2(.-), NO is converted rapidly to pe roxynitrite, ONO2-. This product, which is stable at alkaline pH, was confirmed by gamma-radiolysis of aerated ammonia solutions.