Mechanisms of Acid-Promoted N2 and N2O Generation from NH2NO and NH2NO2.

The effects of water, formic acid, and nitric acid on N2 and N2O generation from NH2NO and NH2NO2 are studied using high-level quantum-chemical calculations. It is shown that the reaction barriers from isolated NH2NO and NH2NO2 are 35.5 and 38.1 kcal/mol, respectively. When the NH2NO and NH2NO2 reactions are examined in the presence of water, formic acid, or nitric acid, the energy barriers are different. The mechanisms of these reactions are revealed through reaction pathway calculations. The isomerization of intermediate HNNOH and HNNOOH molecules, which follows a group rotation mechanism, plays a key role in reactions of isolated NH2NO and NH2NO2. However, the presence of water, formic acid, or nitric acid changes the isomerization mechanism substantially. HNNOH or HNNOOH and the catalyzing molecule form a doubly hydrogen-bonded prereactive complex, which, in turn, facilities hydrogen atom migration (this is denoted as the hydrogen atom migration mechanism). This study demonstrates the feasibility of N2 or N2O generation from NH2NO and NH2NO2 in the presence of water, formic acid, or nitric acid.