Understanding the Physics
and Chemistry of Reaction
Mechanisms from Atomic Contributions: A Reaction Force Perspective
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Abstract
Studying chemical reactions involves the knowledge of
the reaction
mechanism. Despite activation barriers describing the kinetics or
reaction energies reflecting thermodynamic aspects, identifying the
underlying physics and chemistry along the reaction path contributes
essentially to the overall understanding of reaction mechanisms, especially
for catalysis. In the past years the reaction force has evolved as
a valuable tool to discern between structural changes and electrons’
rearrangement in chemical reactions. It provides a framework to analyze
chemical reactions and additionally a rational partition of activation
and reaction energies. Here, we propose to separate these energies
further in atomic contributions, which will shed new insights in the
underlying reaction mechanism. As first case studies we analyze two
intramolecular proton transfer reactions. Despite the atom based separation
of activation barriers and reaction energies, we also assign the participation
of each atom in structural changes or electrons’ rearrangement
along the intrinsic reaction coordinate. These participations allow
us to identify the role of each atom in the two reactions and therfore
the underlying chemistry. The knowledge of the reaction chemistry
immediately leads us to suggest replacements with other atom types
that would facilitate certain processes in the reaction. The characterization
of the contribution of each atom to the reaction energetics, additionally,
identifies the reactive center of a molecular system that unites the
main atoms contributing to the potential energy change along the reaction
path