1H-cyclopenta[8]annulene
CAS and Beilstein name 1H-cyclopentacyclooctene
benzo[22]annulene
CAS and Beilstein name benzocyclodocosene
Contents of Section
FR-2. Ring Systems Used as Components
FR-2.1 Hydrocarbon components
FR-2.1.1 Monocyclic hydrocarbon components
FR-2.1.2 Polyacene components
FR-2.1.3 Polyaphene components
FR-2.1.4 Polyalene components
FR-2.1.5 Polyphenylene components
FR-2.1.6 Polynaphthylene components
FR-2.1.7 Polyhelicene components
FR-2.1.8 Ace....ylene components
FR-2.1.9 Trivially named hydrocarbon components
References for this Section
Continue with FR-2.2 Heterocyclic Components.
The names of polycyclic fused ring systems are derived from those of components which are themselves mono- or poly-cyclic ring systems.
Hydrocarbon parent components are listed in Appendix 1. The components are listed in decreasing order of preference for choice of components (see FR-2.3).
FR-2.1.1 Monocyclic hydrocarbon components
Monocyclic hydrocarbon parent components (other than benzene) are named as [n]annulenes, where n represents the ring size. The corresponding attached component prefix is derived from the appropriate cycloalkane stem with the ending '-a'.
Examples:
benzo[22]annulene
CAS and Beilstein name benzocyclodocosene
Notes
1. In previous versions of these rules (ref 3, A-21.4)) the parent component was named from the cycloalkane stem with the ending '-ene'. This would normally imply one double bond in the ring in contrast to the meaning here of the system with the maximum number of non-cumulative double bonds. Use of the [n]annulene terminology prevents any confusion. The traditional names of the attached components are retained.2. [n]Annuleno is not used as a prefix.
3. The alternative method for the naming of these systems described in rule A-23.5 (ref 3) is abandoned.
4. [n]Annulene with n < 6 is only used as a parent component not for the isolated system.
A hydrocarbon parent component that consists of four or more ortho-fused benzene rings in a straight linear arrangement is named from the numerical prefix (ref 10) denoting the number of benzene rings followed by the ending '-acene' (derived from anthracene). In an attached component prefix the ending '-acene' is changed to '-aceno'. Note that tetracene was called naphthacene in rule A-21.1 (ref 3) and this is still used by CAS and Beilstein.
Example:
FR-2.1.3 Polyaphene components
A hydrocarbon parent component that consists of n ortho-fused benzene rings (n > 3) and comprises two straight linear arrangements of (n+1)/2 and (n+1)/2 (if n is odd) or n/2 and (n/2)+1 rings (if n is even) with a common benzene ring and which make a formal angle of 120o is named by citing the numerical prefix (ref 10) denoting the total number of benzene rings followed by the ending '-aphene' (derived from phenanthrene). In an attached component prefix the ending '-aphene' is changed to '-apheno'.
Examples:
hexaphene
A hydrocarbon parent component that consists of two identical ortho-fused monocyclic hydrocarbon rings is named from the numerical prefix (ref 10) denoting the number of carbon atoms in each ring and the ending '- alene'. The trivial name naphthalene is retained for hexalene. In an attached component prefix the ending '- alene' is changed to '-aleno'.
Examples:
heptalene
octalene
FR-2.1.5 Polyphenylene components
A hydrocarbon parent component that consists of a monocyclic hydrocarbon with an even number of carbon atoms and benzene rings ortho-fused to alternate sides is named from the numerical prefix (ref 10) denoting the number of benzene rings followed by the ending '-phenylene'. In an attached component prefix the ending '-phenylene' is changed to '-phenyleno'. As an exception the first member of the series is called biphenylene instead of diphenylene.
Examples:
triphenylene
FR-2.1.6 Polynaphthylene components
A hydrocarbon parent component that consists of a monocyclic hydrocarbon with an even number of carbon atoms and with naphthalene ring systems 2,3-fused to alternate sides is named from the numerical prefix (ref 10) denoting the number of naphthalene units followed by the ending 'naphthylene'. In an attached component prefix the terminal '-e' is changed to '-o'. The first member of the series (with two naphthalene ring systems) is called dibenzo[b,h]biphenylene and is not used as a component.
Examples:
tetranaphthylene
FR-2.1.7 Polyhelicene components
A hydrocarbon parent component of six or more rings that consists of a benzene ring fused to the 3,4- position of phenanthrene and further benzene rings fused in a similar way is named from the numerical prefix (ref 10) denoting the total number of rings followed by the ending '- helicene'.
Example:
The numbering of these ring systems using FR-5 presents a problem due to ring overlap and that the ring where numbering should start depends on the number of rings present. To circumvent this problem it is recommended that a terminal ring be numbered from 1 to 4 followed in the normal way round the external peripheral atoms followed by the internal peripheral atoms. See 32 in Appendix 1.
Note
Polyhelicene names are not used in CAS index nomenclature.
FR-2.1.8 Ace ....ylene components
A hydrocarbon parent component that consists of a five-membered ring ortho- and peri-fused to naphthalene, anthracene or phenanthrene is named by adding the prefix 'ace-' and changing the ending '-alene', '-acene' or '-ene', respectively to '-ylene'.
FR-2.1.9 Trivially named hydrocarbon components
The trivially named hydrocarbons used as parent components in fusion nomenclature are listed below. The reference numbers refer to the entry in Appendix 1.
acenaphthylene
acephenanthrylene
aceanthrylene
| anthracene | 47 | (see FR-2.1.2 for other straight linear systems) | naphthalene | 57 | |
| azulene | 56 | ovalene | 10 | ||
| benzene | 62 | (see FR-2.1.1 for other monocycles) | perylene | 36 | |
| chrysene | 41 | phenalene | 49 | ||
| coronene | 26 | phenanthrene | 48 | (see FR-2.1.3 for other bent linear systems) | |
| fluoranthene | 46 | picene | 37 | ||
| fluorene | 50 | pleiadene | 38 | ||
| as-indacene | 54 | pyranthrene | 20 | ||
| s-indacene | 53 | pyrene | 42 | ||
| indene | 58 | rubicene | 28 |
anthra from anthracene naphtho from naphthalene
benzo from benzene phenanthro from phenanthrene
Notes
1. Rule A-21.4 (ref 3) also recommended the abbreviation of acenaphthyleno and peryleno to acenaphtho and perylo, which are still used by CAS and Beilstein.2. The non-standard numberings of anthracene and phenanthrene are retained (see Appendix 1).
3. CAS and Beilstein also include trindene (cyclopenta[e]-as-indacene).
3. IUPAC Nomenclature of Organic Chemistry, Sections A and B, 1st edition, 1958; 2nd edition, 1966; 3rd edition (combined with section C), 1971; 4th edition (combined with sections C, D, E, F and H), 1979.
10. IUPAC, Extension of rules A-1.1 and A-2.5 concerning numerical terms used in organic chemical nomenclature, Pure Appl. Chem. 58, 1493-1496 (1986).
Return to home page for Fused Ring Nomenclature.