Computational Investigation of Radical‐ and Catalyst‐Assisted Decomposition of CH2NO• to HCN

Le résumé fourni par la source

Hydrogen cyanide (HCN) is a chemically and prebiotically important molecule found in the Earth's atmosphere and other planetary environments. Previous photochemical studies have proposed that HCN could originate from reactions between methane photolysis products, such as methyl radical (CH3•) and triplet methylene (3CH2), and reactive nitrogen species like atomic nitrogen (N) and nitric oxide (NO). In this study, we introduce a new atmospheric route to HCN formation involving the decomposition of CH2NOX intermediates, which are formed via the recombination of CH2NO• with other atmospheric reactive species (X) such as NO, OH•, and CH3•. Using high‐level quantum chemical calculations [CCSD(T)//M06‐2X/6‐311++G(3df,3pd)], we investigate the mechanism of CH2NOX decomposition towards HCN formation via uncatalyzed and catalyst‐assisted (H2O, NH3, HCl and H2SO4) pathways. Kinetic analysis based on transition state theory (TST) reveals that, while CH2NONO and CH2NOOH exhibit significant kinetic barriers under ambient conditions, CH2NOCH3 undergoes rapid decomposition, particularly when catalyzed by H2SO4. Among all species examined, the H2SO4‐assisted decomposition of CH2NOCH3 shows the highest rate enhancement relative to its uncatalyzed counterpart. This work not only introduces CH2NO• as a novel intermediate in atmospheric nitrogen chemistry but also highlights the key role of CH3• (a methane photolysis product) and H2SO4 in enabling efficient HCN production in both early and modern Earth atmospheres.

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