Rate constant for the NH ₃ + NO ₂ → NH ₂ + HONO reaction: Comparison of kinetically modeled and predicted results

The rate constant for the NH ₃ + NO ₂ ⇌ NH ₂ + MONO reaction (1) has been kinetically modeled by using the photometrically measured NO ₂ decay rates available in the literature. The rates of NO ₂ decay were found to be strongly dependent on reaction (1) and, to a significant extent, on the secondary reactions of NH ₂ with NO _x and the decomposition of HONO formed in the initiation reaction. These secondary reactions lower the values of k ₁ determined directly from the experiments. Kinetic modeling of the initial rates of NO ₂ decay computed from the reported rate equation, - d[NO ₂ ]/dt = k ₁ [NH ₃ ][NO ₂ ] based on the conditions employed led to the following expression: k ₁ = 10 ^11.39 ± ^0.16 e ^{-(12620 ± 240)/T} cm ³ mole ^-1 s ^-1 This result agrees closely with the values predicted by ab initio MO [G2M//B3LYP/6-311G(d,p)] and TST calculations.