As exceptions, Greek capital delta (), followed by superscript locant(s), is used to denote a double bond in a compound named according to Rule B-1.2 if its name is preceded by locants for hetero atoms; and also to denote a double bond uniting components in a assembly of rings (cf. Examples to Rules A-52.1 and C-71.1)

This HTML reproduction of Sections A, B and C of IUPAC "Blue Book" is as close as possible to the published version [see Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F, and H, Pergamon Press, Oxford, 1979. Copyright 1979 IUPAC.] If you need to cite these rules please quote this reference as their source.

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