The stem for six-membered rings depends on the least preferred heteroatom in the ring, i.e., the heteroatom whose name directly precedes the stem. To determine the proper stem for a six-membered ring, select the set below that contains the least preferred heteroatom before consulting the table. For example, the proper stem for the dioxazine ring is found after set 6B, which contains the element nitrogen.

6A: O, S, Se, Te, Bi, Hg

6B: N, Si, Ge, Sn, Pb

6C: B, F, Cl, Br, I, P, As, Sb

This HTML reproduction is as close as possible to the published version [see IUPAC, Commission on Nomenclature of Organic Chemistry. A Guide to IUPAC Nomenclature of Organic Compounds (Recommendations 1993), 1993, Blackwell Scientific publications, Copyright 1993 IUPAC]. If you need to cite these rules please quote this reference as their source.

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