Substitution nomenclature

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The replacement nomenclature , as "a" - nomenclature or replacement nomenclature referred (Engl. Replacement nomenclature ), is a method of systematic designation of heterocyclic compounds. The name of the underlying hydrocarbon is used as a starting point and this is supplemented by preceding "a" terms of the heteroatoms present in the molecule . According to a recommendation by IUPAC , the replacement nomenclature is used for heteromonocycles with a ring size> 10, as well as for simple bridged heterocycles and simple spiroheterocycles. Smaller and condensed heterocycles are named after the Hantzsch-Widman system .

“A” terms for heteroatoms

The “a” terms used as prefixes result from the possible heteroatoms, which are prioritized according to their position in the periodic table . The priority of an element increases with the number of the group in the periodic table . Within a group, the elements with the lower ordinal number have the higher priority.

“A” terms for heteroatoms in decreasing priority
element symbol "A" term element symbol "A" term
1 Iodine I. Ioda 10 Bismuth Bi Bisma
2 oxygen O Oxa 11 Silicon Si Sila
3 sulfur S. Thia 12 Germanium Ge Germa
4th selenium Se Selena 13 tin Sn Stanna
5 Tellurium Te Tellura 14th lead Pb Plumba
6th nitrogen N Aza 15th boron B. Bora
7th phosphorus P Phospha 16 aluminum Al Alumina
8th arsenic As Arsa 17th zinc Zn Zinca
9 antimony Sb Stiba 18th mercury Ed Mercura

If the heteroatom is present as a cation , the last letter “a” of the “a” term is replaced by the ending “onia” (example: nitrogen: aza , nitrogen cation : azonia ). If the heteroatom is present as an anion , the last letter “a” of the “a” term is replaced by the ending “ato” (example: boron: bora , boron anion: borato ).

If the heterocycle contains several heteroatoms, the heteroatom with the higher priority is named first and receives the lowest possible number. If a heteroatom is present several times in the molecule, the corresponding numerical prefix (di-, tri- etc.) is placed in front of the “a” term.

Examples

  • 1-oxa-3-thiacyclopentane
    (Hantzsch-Widman: 1,3-oxathiolane)

  • 1,6-Dioxa-4-aza-9-azonia-5-borato-spiro [4.4] nonane

  • 7-Oxa-1,5-diaza-8-mercura-bicyclo [4.2.0] octane

Individual evidence

  1. ↑ Entry on exchange nomenclature. In: Römpp Online . Georg Thieme Verlag, accessed on March 19, 2019.
  2. ↑ Dieter Hellwinkel: The systematic nomenclature of organic chemistry: Instructions for use . 2nd Edition. Springer-Verlag, Berlin, Heidelberg 1978, ISBN 978-3-540-08796-0 , pp. 44–46 ( limited preview in Google Book Search).
  3. ^ WH Powell: Revision of the extended Hantzsch-Widman system of nomenclature for heteromonocycles . In: Pure and Applied Chemistry . tape 55 , no. 2 , January 1, 1983, p. 409-416 , doi : 10.1351 / pac198855020409 . (accessed via de Gruyter Online).