Term: degenerate rearrangement
https://doi.org/10.1351/goldbook.D01559

Definition:
A molecular rearrangement in which the principal product is indistinguishable (in the absence of isotopic labelling) from the principal reactant. The term includes both 'degenerate intramolecular rearrangements' and reactions that involve intermolecular transfer of atoms or groups ('degenerate intermolecular rearrangements'): both are degenerate isomerizations. The occurrence of degenerate rearrangements may be detectable by isotopic labelling or by dynamic NMR techniques. For example: thesigmatropic rearrangement of hexa-1,5-diene (Cope rearrangement): D01559.png Synonymous but less preferable terms are 'automerization', 'permutational isomerism', 'isodynamic transformation', 'topomerization'.

Related Terms:
1) fluxional (http://doi.org/10.1351/goldbook.F02463).
2) molecular rearrangement (http://doi.org/10.1351/goldbook.M03997).
3) valence isomer (http://doi.org/10.1351/goldbook.V06590).
4) intramolecular (http://doi.org/10.1351/goldbook.I03130).
5) intermolecular (http://doi.org/10.1351/goldbook.I03098).
6) isomerizations (http://doi.org/10.1351/goldbook.I03295).
7) sigmatropic rearrangement (http://doi.org/10.1351/goldbook.S05660).
8) isotopic labelling (http://doi.org/10.1351/goldbook.I03345).
9) rearrangement (http://doi.org/10.1351/goldbook.R05194).
10) automerization (http://doi.org/10.1351/goldbook.A00528).
11) isomerism (http://doi.org/10.1351/goldbook.I03294).
12) transformation (http://doi.org/10.1351/goldbook.T06446).
13) topomerization (http://doi.org/10.1351/goldbook.T06396).

Image: Not defined (https://goldbook.iupac.org/img/inline/D01559.png) 

Source: PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1104 (https://doi.org/10.1351/pac199466051077)

Citation: 'degenerate rearrangement' 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.D01559

License: 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.

Disclaimer: 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.