Quantum Dynamics of Radical Reaction Mechanisms

Radical reaction mechanisms lie at the heart of many chemical processes, from atmospheric chemistry and combustion to synthetic organic transformations and biological oxidations. Quantum dynamics offers a detailed, atomistic view of how unpaired electrons drive bond breaking and formation, capturing phenomena such as tunnelling, nonadiabatic transitions and wavepacket bifurcation. By solving the time‐dependent Schrödinger equation on accurately computed potential energy surfaces, researchers can track how a nascent radical explores its landscape of transition states and intermediates. Such simulations reveal the influence of electronic state crossings—often through conical intersections—on product branching, and quantify nuclear quantum effects that classical kinetics cannot capture. Experimental techniques including femtosecond spectroscopy and high‐resolution scattering complement theoretical work, providing time‐resolved snapshots of radical wavepackets and validating computed rate coefficients and product distributions. Together, these advances afford predictive control over selectivity and yield in processes ranging from fuel combustion to polymerisation and environmental oxidation pathways. The integration of quantum dynamical methods with machine‐learning potential energy surfaces and ultrafast measurements promises a comprehensive framework for understanding and manipulating radical reactivity at the quantum level.

Research from Nature Portfolio

Recent studies have utilised multi‐configuration time‐dependent Hartree simulations on machine‐learned potential energy surfaces to demonstrate significant hydrogen‐atom tunnelling in alkyl radical isomerisation at ambient conditions, altering conventional barrier‐height dependencies in rate predictions. Another investigation combined attosecond electron diffraction with nonadiabatic quantum dynamics to resolve spin‐orbit coupling and intersystem crossing in peroxy radicals, revealing ultrafast population transfer between singlet and triplet states that dictates product partitioning. A third contribution employed wavepacket propagation across conical intersections to show that subtle variations in substituent geometry can steer photolytic radical fragments towards distinct reaction channels, offering a route to photochemical selectivity control.

Quantum Dynamics of Radical Reaction Mechanisms publication trend

The graph below shows the total number of articles in quantum dynamics of radical reaction mechanisms across all publications each year (not limited to Nature Index journals).

Technical terms

Radical: A chemical species with one or more unpaired electrons in its outer shell.

Potential Energy Surface (PES): A multidimensional representation of a system’s energy as nuclear coordinates vary.

Nonadiabatic coupling: Interaction that allows transitions between electronic states during nuclear motion.

Quantum tunnelling: Passage of a particle through an energy barrier lower than its total energy.

Conical intersection: A point where two electronic states become degenerate, enabling rapid nonradiative transitions.

References

1. The Onset of H + Ketene Products from Vinoxy Radicals Prepared by Photodissociation of Chloroacetaldehyde at 157 nm. The Journal of Physical Chemistry A (2016).
2. Tailoring the Mechanistic Pathways and Kinetics of Decomposition of CH3CH2C(O)OCH2CH2O Radical: A DFT Study. Asian Journal of Chemistry (2023).