00133 IUPAC Gold Book - addition reaction 10.1351/goldbook.A00133 A00133 current mentioned: addend 1 A chemical reaction of two or more reacting molecular entities, resulting in a single reaction product containing all atoms of all components, with formation of two chemical bonds and a net reduction in bond multiplicity in at least one of the reactants. The reverse process is called an elimination reaction. The addition may occur at only one site (α-addition, 1/1/addition), at two adjacent sites (1/2/addition) or at two non-adjacent sites (1/3/- or 1/4/addition, etc.). For example: If the reagent or the source of the addends of an addition are not specified, then it is called an addition transformation. addition https://goldbook.iupac.org//terms/view/A00132 cheletropic reaction https://goldbook.iupac.org//terms/view/C01014 chemical reaction https://goldbook.iupac.org//terms/view/C01033 cycloaddition https://goldbook.iupac.org//terms/view/C01496 elimination https://goldbook.iupac.org//terms/view/E02038 molecular https://goldbook.iupac.org//terms/view/M03986 reagent https://goldbook.iupac.org//terms/view/R05190 transformation https://goldbook.iupac.org//terms/view/T06446 α-addition https://goldbook.iupac.org//terms/view/A00001 PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1081 (https://doi.org/10.1351/pac199466051077) https://goldbook.iupac.org/terms/view/A00133/html https://goldbook.iupac.org/terms/view/A00133/json https://goldbook.iupac.org/terms/view/A00133/plain Citation: 'addition reaction' 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.A00133 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. 2026-07-14T03:45:34+00:00