Reaction between N₂O₅ and NH₃ under Tropospheric Conditions: A Quantum Chemical and Chemical Kinetic Investigation

Abstract

The gas-phase reaction of N 2 O 5 with NH 3 under tropospheric conditions has been carried out employing quantum chemical calculations at the CCSD(T)/CBS//MP2/aug-cc-pVTZ level of theory. The activation barrier of the reaction was found to be 13.5 kcal mol −1 with respect to isolated reactants. Chemical kinetic calculations were carried out under pre-equilibrium approximation using transition-state theory employing Eckart tunneling, and the rate coefficient was found to be 1.02 × 10 −24 cm 3 molecule −1 s −1 at 298 K. To check the reliability of the result, calculations have also been carried out using the canonical variational transition-state theory employing both zero-and small-curvature tunneling as well as the master equation. The results obtained from these methods were found to be consistent with those obtained from the transition-state theory. The rate coefficient was found to show positive temperature dependence, and its rate of change with temperature was found to be very similar for all three methods. Further, the pressure dependence of the rate coefficient has been checked and it was found that it shows negligible pressure dependence under tropospheric conditions. Besides, all of the electronic structure calculations have been carried out at the CCSD(T)-F12/cc-pVTZ// M06-2X/aug-cc-pVTZ level of theory and the rate coefficients using all of the above-mentioned kinetic models have been computed using these results. The results were found to match closely with the CCSD(T)//CBS//MP2/aug-cc-pVTZ results.

A Computational Study on the Redox Reactions of Ammonia and Methylamine with Nitrogen Tetroxide

“…We have also compared the kinetics for NH 3 + N 2 O 4 with the analogous NH 3 + N 2 O 5 reaction recently reported by Sarkar and Bandyopadhyay under troposphere conditions. Based on reported relative concentrations of the two oxidants, the former process was estimated to be about 2 orders of magnitude greater in the troposphere.…”

“…During the preparation of this article, for publication, Sarkar and Bandyopadhyay reported in this journal on the reaction of NH 3 with N 2 O 5 , which is relevant to the troposphere NO x chemistry . Their potential energy surface (PES) was characterized at the CCSD­(T)-F12/cc-pVTZ//M06-2X/aug-cc-pVTZ level, and the rate constant predicted with tunneling corrections was 1.0 × 10 –24 cm 3 molecule –1 s –1 at 298 K. The major products of this reaction were predicted to be HNO 3 and H 2 NNO 2 .…”

“…During the preparation of this article, 15 for publication, Sarkar and Bandyopadhyay reported in this journal on the reaction of NH 3 with N 2 O 5 , which is relevant to the troposphere NO x chemistry. 16 Their potential energy surface (PES) was characterized at the CCSD(T)-F12/cc-pVTZ//M06-2X/augcc-pVTZ level, and the rate constant predicted with tunneling corrections was 1.0 × 10 −24 cm 3 molecule −1 s −1 at 298 K. The major products of this reaction were predicted to be HNO 3 and H 2 NNO 2 . We will compare our computed rate constant for the oxidation of NH 3 by NTO via the novel mechanism alluded to above as well as that for the NH 3 + NO 2 reaction for which one of the present authors investigated in detail in conjunction with the HNO x chemistry related to rocket propellant combustion.…”

Possible atmospheric source of NH2SO3H: the hydrolysis of HNSO2 in the presence of neutral, basic, and acidic catalysts

“…These geometrical structures were also in good agreement with earlier findings. 21,28,29,33,34,65 The stabilization energies of (…”

An Exploration of the Hydrogen Bond Donor Ability of Ammonia

“…An atmospherically important reaction between N 2 O 5 and NH 3 to form HNO 3 has been studied theoretically. [4] The initial step of the reaction is the formation of a reactant complex which is stabilised by N À H � � � O H-bond interaction. Thus, investigation of the H-bond donor property of NH 3 is important towards the molecular level understanding of these fundamental reaction pathways.…”