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

Area of Science:

• Atmospheric Chemistry
• Astrobiology
• Quantum Chemistry

Background:

• Hydrogen cyanide (HCN) is crucial for prebiotic chemistry and present in planetary atmospheres.
• Previous models suggested HCN formation from methane photolysis products and nitrogen species.
• An unexplored atmospheric route for HCN production requires investigation.

Purpose of the Study:

• To introduce and investigate a novel atmospheric pathway for hydrogen cyanide (HCN) formation.
• To explore the decomposition mechanisms of CH2NOX intermediates leading to HCN.
• To assess the influence of catalysts on HCN production rates.

Main Methods:

• High-level quantum chemical calculations (CCSD(T)//M06-2X/6311++G(3df,3pd)) were employed.
• Reaction mechanisms for CH2NOX decomposition were studied.
• Kinetic analysis using transition state theory evaluated catalyzed and uncatalyzed pathways.

Main Results:

• A new route involving CH2NOX intermediate decomposition to HCN was identified.
• CH2NOCH3 decomposition is rapid, especially when catalyzed by sulfuric acid (H2SO4).
• H2SO4-catalyzed CH2NOCH3 decomposition shows the highest rate enhancement.

Conclusions:

• CH2NO• is identified as a novel intermediate in atmospheric nitrogen chemistry.
• Methane photolysis products (CH3•) and H2SO4 play key roles in efficient HCN production.
• This pathway is relevant for both early and modern Earth atmospheric conditions.