https://doi.org/10.1351/goldbook.08818
Magnitude of the region in a molecule over which a molecular orbital occupied with delocalized electrons is extended.
Notes:
- 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.