Sometimes the IUPAC name is too verbose despite the structure's high symmetry. If we could use only the first locant of the ("topologically symmetrically") equivalent set of locants, and designate all of them by some symbol (e.g. xallsym, which is too long, and Greek letter sigma has some meanings already, so I will use Greek letter stigma), then we could have

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1,3,5-trinitrohexahydro-s-triazine vs
1ς-trinitrohexahydro-s-triazine or

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naphthalene-1,4,5,8-tetrol vs

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naphthalene-1,2,4,5,8-pentol vs

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naphthalene-1,2,3,6,7-pentol vs

1,5(1,2,3),2,4,6,8,9(1,4),3,7(1,2)-nonabenzenabicyclo[3.3.1]nonaphane vs

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1,2,3,4,5,6-hexachlorobenzene or
hexachlorobenzene vs
1ς-hexachlorobenzene (the name is not convenient in this case)

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1,2,3,4,5,6-hexachlorocyclohexane vs

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1,1,2,2,3,3,4,4,5,5,6,6-dodecachlorocyclohexane or
perchlorocyclohexane vs
(not convenient in this case, but mentioned the special feature, listing two identical sets. Imagine 1ς means 1,2,3,4,5,6; 1ς,ς would mean 1,2,3,4,5,6,1,2,3,4,5,6)

Wrong usage can lead to contadictions/confusion, e.g. 1ς-trichlorobenzene would be illegal, because benzene carbon 1 is equivalent with all other carbons, total 6. But it is distantly similar problem like for with name like 1,2,3-hexachlorobenzene.

Is anyone aware of such feature in any chemical nomenclature?

  • $\begingroup$ "topologically" isn't appropriate here, as this is geometry; topology is a different thing altogether. Also your "pentol" is bad example. $\endgroup$
    – Mithoron
    Apr 27, 2017 at 22:43
  • $\begingroup$ Mithoron, could you explain what bad do you see on the pentol example? The "stigma" apples to the single locant immediately before the exponent, of course; and to the parent structure without any substituent that are defined by the prefixes. $\endgroup$
    – mykhal
    Apr 28, 2017 at 4:48
  • $\begingroup$ gilleain, it means "all equivalent atoms", so 1* on cyclooctane means all eight carbons, so you cannot use this "stigma" for the mentioned set of positions. $\endgroup$
    – mykhal
    Apr 28, 2017 at 4:51
  • $\begingroup$ Mithoron, geometry is much less appropriate term here, since you can draw cyclohexane as non-regular distorted hexagon, but the atom equivalence does not change. $\endgroup$
    – mykhal
    Apr 28, 2017 at 5:06


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