Extension and Revision of the von Baeyer System for Naming Polycyclic Compounds (Including Bicyclic Compounds)
(IUPAC Recommendations 1999)


Continued from VB-1 to VB-5

Contents of Section

VB-6 Naming Hydrocarbon Polycyclic Systems

VB-6 Naming Hydrocarbon Polycyclic Systems

Any rings not described by the bicyclic system are defined by citing the number of atoms making up each secondary bridge. The locants of the two attachment points of each secondary bridge are cited as a pair of superscript locants (lower first) separated by a comma. The numbers indicating independent secondary bridges are cited in decreasing order.

The name of the polycyclic hydrocarbon is then constructed by:

a prefix indicating the number of rings (tricyclo, tetracyclo, etc.);

numbers indicating the bridge lengths (with the appropriate superscript locants in the case of secondary bridges) separated by full stops and placed in square brackets (e.g. [,4]); error details

and the name of the parent hydrocarbon indicating the number of ring atoms.



not tricyclo[]octadecane

NoteThe independent secondary bridge C-18 requires the superscript locants 1,11 to indicate its attachment.

Independent secondary bridges are cited before dependent secondary bridges. The numbers indicating dependent secondary bridges are cited in decreasing order.


(011,25 is a dependent secondary bridge)

(113,28 is a dependent secondary bridge)

Note The sum of the numbers indicating the atoms in the bridges comprising the main ring, the main bridge and all secondary bridges plus two will equal the number of skeletal atoms present e.g. in the example above (13 + 7 + 4 + 3 + 1) + 2 = 30 hence triacontane.

If there is a choice of names the following criteria are considered in order until a decision is made.

VB-6.1 The main ring shall be divided as symmetrically as possible by the main bridge.


not tricyclo[,6]undecane (4.3 more symmetric than 5.2)

VB-6.2 If there is a choice of independent secondary bridges the first cited shall be as long as possible. Then if relevant the second cited independent secondary bridge shall be as long as possible, etc.


not tetracyclo[,9.223,25]octacosane ( is higher than

VB-6.3 The number of dependent secondary bridges is kept to a minimum.


not tetracyclo[,4.06,13]tridecane (06,13 is a dependent secondary bridge)
nor tetracyclo[,6.02,5]tridecane (see VB-6.4)

VB-6.4 The superscript locants of the secondary bridges shall be as small as possible when considered as a set in ascending numerical order, a decision being made at the first point of difference.


not tricyclo[,9]tridecane (3,11 is lower than 5,9)

not tricyclo[,7]dodecane (1,5 is lower than 1,7)
nor tricyclo[,6]dodecane (4.4 is more symmetric than 5.3 for main ring, see VB-6.1)

not pentacyclo[,8.03,5.07,9]decane (2,3,4,7,8,10 is lower than 2,3,5,7,8,9)
nor pentacyclo[,4.05,9.08,10]decane (2,3,4,7,8,10 is lower than 2,4,5,8,9,10)
nor pentacyclo[,5.04,10.07,9]decane (2,3,4,7,8,10 is lower than 3,4,5,7,9,10)

VB-6.5 The superscript locants shall be as small as possible when considered in the order of citation in the name.


not tetracyclo[,12.12,6]heptadecane (2,6,8,12 is lower than 8,12,2,6)

not pentacyclo[,8.03,7.04,6]octane (2,4,3,7,6,8 is lower than 2,8,3,7,4,6)

not tetracyclo[,14.13,31]tritriacontane (3,14,8,31 is lower than 8,14,3,31)
nor tetracyclo[,9.114,30]tritriacontane (3,8,14,31 is lower than 3,9,14,30, see VB-6.4)
nor tetracyclo[,14.19,30]tritriacontane 3,8,14,31 is lower than 3,9,14,30, see VB-6.4)

not pentacyclo[,19.17,38.114,36]hentetracotane (2,14,7,38,19,36 is lower than 2,19,7,38,14,36)
nor pentacyclo[,14.12,38.119,36]hentetracotane (2,14,7,38,19,36 is lower than 7,14,2,38,19,36)
nor pentacyclo[,19.12,38.114,36]hentetracotane (2,14,7,38,19,36 is lower than 7,19,2,38,14,36)
nor pentacyclo[,7.314,19.136,39]hentetracotane ( is higher than, see VB-6.2)

Continued with VB-7
Return to von Baeyer Nomenclature home page.