Exclusive roaming mechanism for the Cl + C₂H₂→C₂H + HCl bimolecular reaction

Area of Science:

• Chemical Dynamics
• Reaction Mechanisms
• Computational Chemistry

Background:

• Conventional bimolecular reactions typically involve direct transition states or potential energy wells.
• Nontraditional reaction pathways, such as roaming mechanisms, are gaining increasing attention in chemical dynamics.

Purpose of the Study:

• To investigate the reaction dynamics of Cl + C2H2 → C2H + HCl.
• To determine the dominant reaction mechanisms and challenge conventional understanding.

Main Methods:

• Full-dimensional dynamics simulations were performed.
• A machine learning-based potential energy surface was utilized for accurate calculations.

Main Results:

• The Cl + C2H2 reaction is predominantly governed by two roaming mechanisms: Cl-roaming and H-roaming.
• These roaming pathways, involving transient adducts and atom migration, account for nearly 100% of the total reaction yield.
• Distinct energy and angular distributions were observed for the roaming pathways.

Conclusions:

• The study challenges the traditional view of bimolecular reactions proceeding solely through conventional transition states.
• Roaming mechanisms play a crucial role in the Cl + C2H2 reaction dynamics.
• Considering nontraditional pathways is essential for accurate rate constant predictions and mechanistic insights in reaction dynamics.