Title: Möbius aromaticity
Long Title: IUPAC Gold Book - Möbius aromaticity
DOI: 10.1351/goldbook.M03957
Status: current

Definition
A monocyclic array of orbitals in which there is a single out-of-phase overlap (or, more generally, an odd number of out-of-phase overlaps) reveals the opposite pattern of aromatic character to Hückel systems; with \(4\, n\) electrons it is stabilized (aromatic), whereas with \(4\, n+2\) it is destabilized (antiaromatic). In the excited state \(4\, n+2\) Möbius $\ce{\uppi\!\mbox{-}electron}$ systems are stabilized, and \(4\, n\) systems are destabilized. No examples of ground-state Möbius $\ce{\uppi\!\mbox{-}electron}$ systems are known, but the concept has been applied to transition states of pericyclic reactions. The name is derived from the topological analogy of such an arrangement of orbitals to a Möbius strip.

Related Terms
- Hückel (4<em>n</em> + 2) rule: https://goldbook.iupac.org//terms/view/H02867
- aromatic: https://goldbook.iupac.org//terms/view/A00441
- excited state: https://goldbook.iupac.org//terms/view/E02257
- pericyclic reactions: https://goldbook.iupac.org//terms/view/P04491
- transition states: https://goldbook.iupac.org//terms/view/T06468

Source
- PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1141 (https://doi.org/10.1351/pac199466051077)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/M03957/html
- json: https://goldbook.iupac.org/terms/view/M03957/json
- xml: https://goldbook.iupac.org/terms/view/M03957/xml

Citation: Citation: 'Möbius aromaticity' 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.M03957
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Accessed: 2025-11-19T01:12:58+00:00