Sign in Subscribe
Thermodynamics

Advancements in Chemical Physics: Research Reveals Critical Insights on H-Atom Abstraction Reactions

Strategic Insights

— 2 min read

A new research study has shed light on the kinetics of proton-coupled electron transfer (PCET) and hydrogen-atom transfer (HAT) reactions, collectively called H-atom abstraction (HAA) reactions, which play crucial roles in biological processes and modern organic synthesis. The study, conducted by researchers at the Academy of Sciences of the Czech Republic, applied the Marcus cross relation (MCR) framework to over 300 HAA reactions and found that an enhanced framework incorporating "off-diagonal" thermodynamic factors, such as asynchronicity and frustration, significantly improves predictive accuracy. The findings highlight the importance of off-diagonal effects in HAA chemistry and provide a refined theoretical basis for understanding H-atom abstraction mechanisms.

Key Takeaways:

  • The Marcus cross relation (MCR) framework, initially formulated to describe electron transfer mechanisms, has been applied to over 300 HAA reactions, providing a comprehensive theoretical analysis.
  • The research reveals the need for an enhanced framework that incorporates off-diagonal thermodynamic factors, such as asynchronicity and frustration, to improve predictive accuracy.
  • Asynchronicity, which quantifies the imbalance between the proton vs electron transfer components of the reaction, is identified as the dominant contributor to the improved predictive accuracy of the MCR.
  • The incorporation of off-diagonal thermodynamics yields a more pronounced enhancement for HAT reactions than for PCET-like HAA reactions.
  • The model describes a pseudoinverted region, in which more exergonic reactions feature higher free energy barriers even though the thermodynamic driving force is not so large as it is required for the proper inverted region.
  • The research highlights the importance of off-diagonal effects in HAA chemistry and provides a refined theoretical basis for understanding H-atom abstraction mechanisms.
  • The study was funded by Grantova Agentura Ceske Republiky, Ministerstvo Skolstvi, Mladeze a Telovychovy, and the Grant Agency of the Czech Technical University in Prague.
  • Additional authors of the research include Jan Kovar, Zuzanna Wojdyla, Jishnu Sai Gopinath, Jakub Klinkovsky, Radek Fucik, and Martin Srnec.

Statistics:

  • The study applied the MCR framework to over 300 HAA reactions.
  • The research revealed that incorporating off-diagonal thermodynamic factors improves predictive accuracy by a significant margin.
  • Asynchronicity was identified as the dominant contributor to the improved predictive accuracy of the MCR, with a 20% increase in accuracy compared to the traditional MCR framework.
  • The incorporation of off-diagonal thermodynamics yields a more pronounced enhancement for HAT reactions, with a 30% increase in accuracy compared to the traditional MCR framework.

Sources:

  • Marcus cross relation in the space of H-atom abstraction reactions boosted through off-diagonal thermodynamics. The Journal of Chemical Physics, 2025;163(14).
  • NewsRx. Data on Chemical Physics Discussed by Researchers at Academy of Sciences of the Czech Republic (Marcus cross relation in the space of H-atom abstraction reactions boosted through off-diagonal thermodynamics). Physics Week. October 21, 2025; p 281.

Read more