Comprehensive assessment of atmospheric interactions between Criegee intermediate and simplest Imine (CH2NH) in gas and aqueous phase environments

The simplest Criegee intermediate (CH₂OO), produced through the ozonolysis (O₃) of ethylene in the Earth's troposphere, plays a crucial role as a precursor in new particle formation (NPF) and secondary organic aerosols (SOA). Recent experimental and theoretical findings suggest that Criegee intermediate (CI) with organic acid, carbonyl, and amines is important for organic aerosol formation. However, the reaction of CI with imine, especially methanimine (CH₂NH), has not been reported so far. The mechanism for CH₂OO + CH₂NH and CH₂OO + CH₂NH (+ H₂O) was studied using ab initio/MD. Our results indicate that the rate constants for the CH₂OO + CH₂NH reaction fall within the range of CH₂OO + CH₂O and CH₂OO + CH₂CH₂ reaction systems. The product branching ratio analysis indicates that cy-H₂C(OO)NCH₂ (IM_n) and formimidic acid (NHCHOH) are the primary products in the gas phase reaction of CH₂OO + CH₂NH, irrespective of temperature. Notably, the involvement of water in the reaction facilitates the formation of significant pressure-dependent products, such as N-(hydroxymethyl)formamide (HMF_n) and IM_n. Born-Oppenheimer Molecular Dynamics (BOMD) simulations provide strong evidence for IM_n formation in both the gas phase and the air-water interface, with the reaction proceeding more at the interface. Furthermore, BOMD simulations of CH₂OO and CH₂NH interactions on water droplet surfaces highlight the generation of water-mediated loop-structured products, including N-hydroxyethanimine (H₂C = N-CH₂-OOH) and HMHP (OH-CH₂-OOH). This study highlights the potential significance of Criegee-Imine interactions in driving secondary aerosol formation, particularly in areas with elevated nitrogen-based emissions. The findings of this study may offer valuable insights into the CI-imine chemical processes in these regions.