{"term":{"id":"05164","title":"reacting bond rules","longtitle":"IUPAC Gold Book - reacting bond rules","doi":"10.1351\/goldbook.R05164","code":"R05164","status":"current","definitions":[{"id":1,"text":"For an internal motion of a molecular entity corresponding to progress over a transition state (energy maximum), any change that makes the motion more difficult will lead to a new molecular geometry at the energy maximum, in which the motion has proceeded further. Changes that make the motion less difficult will have the opposite effect. (This rule corresponds to the Hammond principle).For an internal motion of a molecular entity that corresponds to a vibration, any change that tends to modify the equilibrium point of the vibration in a particular direction will actually shift the equilibrium in that direction.Effects on reacting bonds (bonds made or broken in the reaction) are the most significant. The bonds nearest the site of structural change are those most strongly affected.","links":[{"term":"Hammond principle","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/H02734"},{"term":"More O'Ferrall–Jencks diagram","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/M04030"},{"term":"molecular entity","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/M03986"},{"term":"transition state","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/T06468"}],"sources":["PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1158 (https:\/\/doi.org\/10.1351\/pac199466051077)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/R05164\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/R05164\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/R05164\/plain"},"citation":"Citation: 'reacting bond rules' 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.R05164","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":"2026-04-27T16:48:16+00:00"}}