00746 IUPAC Gold Book - Brønsted relation 10.1351/goldbook.B00746 B00746 current mentioned: catalysis law 1 The term applies to either of the equations: \[\frac{k_{\rm{HA}}}{p} = G\left ( \frac{q\ K_{\rm{HA}}}{p} \right )^{\alpha}\] \[\frac{k_{\rm{A}}}{q} = G\left ( \frac{q\ K_{\rm{HA}}}{p} \right )^{-\beta} \] (or their logarithmic forms) where \(\alpha\), \(\beta\) and \(G\) are constants for a given reaction series (\(\alpha\) and \(\beta\) are called 'Brønsted exponents'), \(k_{\rm{HA}}\) and \(k_{\rm{A}}\) are catalytic coefficients (or rate coefficients) of reactions whose rates depend on the concentrations of $\ce{HA}$ and/or of $\ce{A^{-}}$. \(K_{\rm{HA}}\) is the acid dissociation constant of the acid $\ce{HA}$, \(p\) is the number of equivalent acidic protons in the acid $\ce{HA}$, and \(q\) is the number of equivalent basic sites in its conjugate base $\ce{A^{-}}$. The chosen values of \(p\) and \(q\) should always be specified. (The charge designations of $\ce{H}$ and $\ce{A}$ are only illustrative.) The Brønsted relation is often termed the 'Brønsted catalysis law' (or the 'Catalysis law'). Although justifiable on historical grounds, this name is not recommended, since Brønsted relations are known to apply to many uncatalysed and pseudo-catalysed reactions (such as simple proton (hydron) transfer reactions). The term 'pseudo-Brønsted relation' is sometimes used for reactions which involve nucleophilic catalysis instead of acid–base catalysis. Various types of Brønsted parameters have been proposed such as \(\beta_{\rm{lg}}\), \(\beta_{\rm{nuc}}\), \(\beta_{\rm{eq}}\) for leaving group, nucleophile and equilibrium constants, respectively. Catalysis law https://goldbook.iupac.org//terms/view/C00875 catalysis https://goldbook.iupac.org//terms/view/C00874 catalytic coefficients https://goldbook.iupac.org//terms/view/C00885 dissociation https://goldbook.iupac.org//terms/view/D01801 leaving group https://goldbook.iupac.org//terms/view/L03493 linear free-energy relation https://goldbook.iupac.org//terms/view/L03551 nucleophilic catalysis https://goldbook.iupac.org//terms/view/N04250 proton (hydron) transfer reactions https://goldbook.iupac.org//terms/view/P04915 PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1091 (https://doi.org/10.1351/pac199466051077) PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 154 (https://doi.org/10.1351/pac199668010149) https://goldbook.iupac.org/terms/view/B00746/html https://goldbook.iupac.org/terms/view/B00746/json https://goldbook.iupac.org/terms/view/B00746/plain Citation: 'Brønsted relation' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.B00746 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. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . 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. 2026-06-28T13:34:13+00:00