spiro union

also defines: free spiro union, spiro atom
https://doi.org/10.1351/goldbook.S05884
A union formed by a single atom which is the only common member of two rings. The common atom is designated as the spiro atom. A free spiro union is one which constitutes the only union direct or indirect between the two rings.
Source:
Blue Book, p. 37 [Terms] [Book]
Citation: 'spiro union' 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.S05884 RIS BibTex EndNote
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