What is it about?

The concept of reaction extent (the progress of a reaction, advancement of the reaction, etc.) was introduced around 100 years ago. Most of the literature provides a definition for the exceptional case of a single reaction step or gives an implicit definition. Starting from the standard definition by IUPAC, we extend the definition of the reaction extent for an arbitrary number of species and (reversible and irreversible) reaction steps. The new general, explicit definition is also valid for non-mass action kinetics. Our approach tries to adhere to the customs of chemists and be mathematically correct simultaneously. The main advantage of the new definition of reaction extent is that by knowing the kinetic model of a reacting system one can now calculate not only the time evolution of the concentration of each reacting species but also the number of occurrences of the individual reaction events.

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Why is it important?

This new possibility provides a unique and useful numerical tool for the large community of researchers who study and analyze complex reaction networks, for example, in combustion chemistry, biochemical systems, and atmospheric chemistry.


We hope that the new definition will help researchers to gain more insight into the mechanism of complex reaction networks by finding out the most frequent reaction pathways, for example, in the metabolism of a drug in our body or in the complex combustion processes of jet engines, etc.

Vilmos Gáspár
Eotvos Lorand Tudomanyegyetem

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This page is a summary of: Reaction extent or advancement of reaction: A definition for complex chemical reactions, Chaos An Interdisciplinary Journal of Nonlinear Science, April 2023, American Institute of Physics,
DOI: 10.1063/5.0130349.
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