{"term":{"id":"00079","title":"acidity","longtitle":"IUPAC Gold Book - acidity","doi":"10.1351\/goldbook.A00079","code":"A00079","status":"current","definitions":[{"id":1,"text":"Of a compound: For Brønsted acids the tendency of a compound to act as a hydron donor. It can be quantitatively expressed by the acid dissociation constant of the compound in water or some other specified medium. For Lewis acids it relates to the association constants of Lewis adducts and π adducts.Of a medium: The use of the term is mainly restricted to a medium containing Brønsted acids, where it means the tendency of the medium to hydronate a specific reference base. It is quantitatively expressed by the appropriate acidity function.","links":[{"term":"Brønsted acids","url":"https:\/\/goldbook.iupac.org\/terms\/view\/B00744"},{"term":"Lewis acids","url":"https:\/\/goldbook.iupac.org\/terms\/view\/L03508"},{"term":"Lewis adducts","url":"https:\/\/goldbook.iupac.org\/terms\/view\/L03510"},{"term":"acidity function","url":"https:\/\/goldbook.iupac.org\/terms\/view\/A00081"},{"term":"association","url":"https:\/\/goldbook.iupac.org\/terms\/view\/A00472"},{"term":"dissociation","url":"https:\/\/goldbook.iupac.org\/terms\/view\/D01801"},{"term":"hydron","url":"https:\/\/goldbook.iupac.org\/terms\/view\/H02904"},{"term":"π adducts","url":"https:\/\/goldbook.iupac.org\/terms\/view\/A04388"}],"sources":["PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1081 (https:\/\/doi.org\/10.1351\/pac199466051077)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/A00079\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/A00079\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/A00079\/plain"},"citation":"Citation: 'acidity' 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.A00079","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.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","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.","accessed":"2026-05-10T04:14:32+00:00"}}