Dekalin

Cis-decalin-3D-balls.png
Ball-and-stick model of cis-decalin (cis-decahydronaphthalene)

Decahydronaphthalene.svg
Författare/Upphovsman: Hbf878, Licens: CC0
Chemical structure of decahydronaphthalene, a.k.a. Decalin; carbons numbered according to different IUPAC numbering rules.

The blue numbers depict the IUPAC rules for numbering of fused polycyclic hydrocarbons. This nomenclature is preferred for polycylics consisting of at least two fused rings with a circumference of at least five atoms each (see here, p.90).

The grey numbers depict the numbering according to the von-Baeyer nomenclature for polycyclics. In principle, this nomenclature can also be applied to decahydronaphthalene, which would be called bicyclo[4.4.0]decane. In the case of decahydronaphthalene the blue numbering variant is preferred because decahydronaphthalene consists of two fused cycles with a circumference of 6 atoms each.