Term: protophilicity
https://doi.org/10.1351/goldbook.08199

Definition:
Special case of nucleophilicity, describing the relative rates of reactions of a series of Lewis bases with a common Brønsted acid. This term has the advantage over the commonly used "kinetic basicity" that philicity and fugality are associated with kinetics, while acidity and basicity are associated with thermodynamics.

Link: 

Source: PAC, 2022, 94, 353. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 2021)' on page 488 (https://doi.org/10.1515/pac-2018-1010)

Citation: 'protophilicity' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.08199

License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms.

Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.