08969 IUPAC Gold Book - secondary species 10.1351/goldbook.08969 08969 current 1 Species formed by the rearrangement or fragmentation of a primary species that is capable of initiating a polymerization. The term 'secondary species' is also used to designate a species centred on a secondary carbon atom, e.g., a propan-2-yl radical. primary species https://goldbook.iupac.org//terms/view/08965 PAC, 2022, 94, 1093. 'Terminology for chain polymerization (IUPAC Recommendations 2021)' on page 1125 (https://doi.org/10.1515/pac-2020-1211) https://goldbook.iupac.org/terms/view/08969/html https://goldbook.iupac.org/terms/view/08969/json https://goldbook.iupac.org/terms/view/08969/plain Citation: 'secondary species' 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.08969 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. 2026-08-04T17:45:22+00:00