08818 IUPAC Gold Book - extent of electron delocalization 10.1351/goldbook.08818 08818 current synonym: effective conjugation length 1 Magnitude of the region in a molecule over which a molecular orbital occupied with delocalized electrons is extended. In a small molecule, the extent of electron delocalization is usually quantified by the number of delocalized electrons included in the extended orbital or by the number of bonds or atoms or both over which the extended molecular orbital is spread. In a larger molecule or macromolecule, delocalized electrons are mostly divided over several to many extended orbitals of various magnitudes separated by orbitals where electrons are practically localized. Therefore, the average number of delocalized electrons per one extended orbital, or the average number of bonds or atoms or both over which a mean extended orbital is spread, are used as a measure of the extent of the electron delocalization. The extent of electron delocalization in a conjugated molecule is often termed effective conjugation length or effective extent of conjugation. delocalized electrons https://goldbook.iupac.org//terms/view/08789 PAC, 2022, 94, 15. 'Glossary of terms relating to electronic, photonic and magnetic properties of polymers (IUPAC Recommendations 2021)' on page 31 (https://doi.org/10.1515/pac-2020-0501) https://goldbook.iupac.org/terms/view/08818/html https://goldbook.iupac.org/terms/view/08818/json https://goldbook.iupac.org/terms/view/08818/plain Citation: 'extent of electron delocalization' 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.08818 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. 2026-06-04T12:47:18+00:00