What is it about?

Substituents can be introduced into molecules to provide them different physical and chemical properties. Here, a theory to understand and quantify this effect is developed in terms of the mechanical work developed by the forces that substituents induce over the rest of the molecule. Additionally, we propose a physical interpretation of the empirical Hammett equation, a seminal linear free-energy relationship in the field of organic chemistry.

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Why is it important?

The substituent-induced force theory permits to understand the substituent effect with unprecedented details, allowing to determine its effect on the global reaction energy, but also to understand what coordinates are contributing in increasing or decreasing this energy. Moreover, it permits to provide a non-empirical explanation to the Hammett equation, which has been used over decades by chemist, and that is still a useful tool to quantify and predict the substituent effect.


This first report on the substituent induced forces will open the possibility to deeply investigate the extension of these formalism to more complex chemical systems, including biological molecules (DNA, proteins,…), inorganic systems, or excited states. These advances will eventually permit to extent the concept of chemical substituent to different chemical structures.

Luis Manuel Frutos
Universidad de Alcalá

Read the Original

This page is a summary of: The concept of substituent-induced force in the rationale of substituent effect, The Journal of Chemical Physics, June 2021, American Institute of Physics, DOI: 10.1063/5.0052836.
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