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Fused Polycyclic Hydrocarbons

Rule A-23. Hydrogenated Compounds

23.1 - The names of "ortho-fused" or "ortho- and peri-fused" polycyclic hydrocarbons with less than maximum number of non-cumulative double bonds are formed from a prefix "dihydro-", "tetrahydro-", etc., followed by the name of the corresponding unreduced hydrocarbon. The prefix "perhydro-" signifies full hydrogenation. When there is a choice for H used for indicated hydrogen it is assigned the lowest available number.

Examples to Rule A-23.1


The following names are retained:

23.2 - When there is a choice, the carbon atoms to which hydrogen atoms are added are numbered as low as possible.

Examples to Rule A-23.2

23.3 - Substituted polycyclic hydrocarbons are named according to the same principles as substituted monocyclic hydrocarbons (see Rules A-12 and A-61).

23.5 (Alternate to part of Rule A-23.1) - The names of "ortho-fused" polycyclic hydrocarbons which have (a) less than the maximum number of non-cumulative double bonds, (b) at least one terminal unit which is most conveniently named as an unsaturated cycloalkane derivative, and (c) a double bond at the positions where rings are fused together, may be derived by joining the name of the terminal unit to that of the other component by means of a letter "o" with elision of a terminal "e". The abbreviations for fused aromatic systems laid down in Rule A-21.4 are used, and the exceptions of Rule A-23.1 apply.

Examples to Rule A-23.5

See Recommendations'93 R-2.4.1, R-9.1, Tables 20 and 20(a)

Radical Names from Trivial and Semi-trivial Names
Radical Names for Fused Cyclic Systems with Side Chains


This HTML reproduction of Sections A, B and C of IUPAC "Blue Book" is as close as possible to the published version [see Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F, and H, Pergamon Press, Oxford, 1979. Copyright 1979 IUPAC.] If you need to cite these rules please quote this reference as their source.

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