Term: fluxional
https://doi.org/10.1351/goldbook.F02463

Definition:
A chemical species is said to be fluxional if it undergoes rapid degenerate rearrangements (generally detectable by methods which allow the observation of the behaviour of individual nuclei in a rearranged chemical species, e.g. NMR, X-ray). Example: bullvalene (1 209 600 interconvertible arrangements of the ten CH groups). F02463.png The term is also used to designate positional change among ligands of complex compounds and organometallics. In these cases, the change is not necessarily degenerate.

Related Terms:
1) valence tautomerization (http://doi.org/10.1351/goldbook.V06591).
2) chemical species (http://doi.org/10.1351/goldbook.CT01038).
3) degenerate rearrangements (http://doi.org/10.1351/goldbook.D01559).
4) ligands (http://doi.org/10.1351/goldbook.L03518).

Image: Not defined (https://goldbook.iupac.org/img/inline/F02463.png) 

Source: PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1115 (https://doi.org/10.1351/pac199466051077)

Citation: 'fluxional' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.F02463

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