Term: intrinsic reaction coordinate https://doi.org/10.1351/goldbook.IT07057 Definition: A minimum-energy reaction path on a potential energy surface in mass-weighted coordinates, connecting reactants to products via the transition state. Related Terms: 1) minimum-energy reaction path (http://doi.org/10.1351/goldbook.M03931). 2) transition state (http://doi.org/10.1351/goldbook.T06468). Source: PAC, 1999, 71, 1919. 'Glossary of terms used in theoretical organic chemistry' on page 1947 (https://doi.org/10.1351/pac199971101919) Citation: 'intrinsic reaction coordinate' 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.IT07057 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.