THEORETICAL STUDY OF HONO REACTIONS WITH H, OH, NO AND NH2 RADICALS

Abstract

Four HONO reactions of importance in the combustion of nitramines involving H, OH, NO and NH2 have been studied by ab initio molecular orbital calculations. The results of these calculations, using the Gaussian-2 and modified Gaussian-2 methods, indicate that all of the reactions except NH2 + HONO occur by both direct abstraction and indirect metathetical reactions. Take the H + HONO reaction, for example, the direct abstraction process producing H2 + NO2 appears to be the the least important channel, whereas the attack of the H atom at the N site producing HNO + OH via the excited HN(O)OH intermediate is the dominant channel. The theoretically computed molecular structures, vibrational frequencies and energies for the reactants and transition states were used to calculate rate constants for different product channels of these reactions employing the conventional transition-state theory or the canonical variational transition-state theory (depending on reaction barriers involved) for direct abstraction reactions and using the RRKM theory for complex-forming indirect metathetical processes.