NOVEL BIMOLECULAR REACTIONS BETWEEN NH3 AND HNO3 IN THE GAS-PHASE

High-level molecular orbital calculations have been performed in the f ramework of the G2M method to explore the reactivity between NH3 and H NO3, key molecular reactants in ammonium nitrate and ammonium nitramid e systems. Two nonionic molecular reaction channels have been identifi ed with a similar reaction barrier, 46 kcal/mol. One channel occurring via a four-member-ring transition state produces H2NNO2 + H2O (1), an d the other, taking place via a five-member-ring transition state, yie lds H2NONO + H2O(2). A transition-state theory calculation employing t he predicted energies and molecular parameters gave rise to the rate c onstants k(1) = 0.81T(3.47)e(-21670)/T and k(2) = 23.2T(3.50)e(-22610) /T for the temperature range 300-3000 K in units of cm(3)/(mol.s). In addition to the reactants, products, and transition states associated with the two reaction channels, several local minima (or molecular com plexes) and secondary reaction products derived from the structural re arrangement of some of the molecular complexes, such as H3NO and H2NOH , have been identified and their energies calculated at the G2M level of theory.