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).
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.
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1115
