Also contains definitions of: free spiro union, spiro atom
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.
Cite as: IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook.