kinetics of the CHNH + NO reaction: formation of nitramines and -alkyl nitroxides.

This study provides a detailed understanding of how the reaction between CHNH, one of the primary products of the CHNH + OH/Cl reactions, and NO occurs in the atmosphere since the reaction is expected to be a dominant sink for the tropospheric CHNH radical. First, we focus on the reaction of the aminyl radical CHNH with NO, complementing the known reaction between CHNH and NO, to provide the overall picture of the CHNH + NO system. The reaction was meticulously examined across the extended range of temperature (298-2000 K) and pressure (0.76-76 000 torr) using quantum chemistry calculations and kinetic modeling based on the framework of the Rice-Ramsperger-Kassel-Marcus (RRKM)-based master equation. Highly correlated electronic structure calculations unveil that the intricate reaction mechanism of the CHNH + NO reaction, which can proceed through O-addition or N-addition to form NO, encompasses numerous steps, channels, and various intermediates and products. The temperature-/pressure-dependent kinetic behaviors and product distribution of the CHNH + NO reaction are revealed under atmospheric and combustion conditions. The main products under atmospheric conditions are found to be CHNHO and NO, as well as CHNHNO, while under combustion conditions, the primary products are only CHNHO and NO. Given its stability under ambient conditions, CHNHNO, a nitramine, is believed to have the potential to induce DNA damage, which can ultimately result in severe cancers. Secondly, by building upon prior research on the CHNH + NO system, this study shows that the reaction of CHNH with NO holds greater importance in urban areas with elevated NO emissions than other oxidants like O. Furthermore, this reaction occurs swiftly and results in the creation of various compounds, such as the carcinogenic nitrosamine (CHNHNO), carcinogenic nitramine (CHNHNO), CHNNOH, (CHNN + HO) and (CHNHO + NO).