Hydrocarbon Ring Assemblies

Hydrocarbon Ring Assemblies

Rule A-51. Definition 

51.1 - Two or more cyclic systems (single rings or fused systems) which are directly joined to each other by double or single bonds are named "ring assemblies" when the number of such direct ring junctions is one less than the number of cyclic systems involved.

Examples to Rule A-51.1

See Recommendations'93 R-2.4.4

Rule A-52. Two Identical Ring Systems 

52.1 - Assemblies of two identical cyclic hydrocarbon systems are named in either of two ways: (a) by placing the prefix "bi-" before the name of the corresponding radical, or (b) for systems joined by a single bond by placing the prefix "bi-" before the name of the corresponding hydrocarbon. In each case, the numbering of the assembly is that of the corresponding radical or hydrocarbon, one system being assigned unprimed numbers and the other primed numbers. The points of attachment are indicated by placing the appropriate locants before the name.

Examples to Rule A-52.1

52.2 - If there is a choice in numbering, unprimed numbers are assigned to the system which has the lower-numbered point of attachment.

Example to Rule A-52.2

52.3 - If two identical hydrocarbon systems have the same point of attachment and contain substituents at different positions, the locants of these substituents are assigned according to Rule A-2.2; for this purpose an unprimed number is considered lower than the same number when primed. Assemblies of primed and unprimed numbers are arranged in ascending numerical order.

Examples to Rule A-52.3

52.4 - The name "biphenyl" is used for the assembly consisting of two benzene rings.

Examples to Rule A-52.4

See Recommendations'93 R-2.4.4

Rule A-53. Non-identical Ring Systems 

53.1 - Other hydrocarbon ring assemblies are named by selecting one ring system as the base component and considering the other systems as substituents of the base component. Such substituents are arranged in alphabetical order. The base component is assigned unprimed numbers and the substituents are assigned numbers with primes. 53.2 - The base component is chosen by considering the following characteristics in turn until a decision is reached: 
(a) The system containing the larger number of rings.

Examples to Rule A-53.2(a)

(b) The system containing the larger ring.

Examples to Rule A-53.2(b)

(c) The system in the lowest state of hydrogenation (see also Part .3 of this rule).

Example to Rule A-53.2(c)

(d) The order of ring systems as set forth in the list of Rule A-21.1.53.3 - Compounds covered by Part .2(c) of this rule may also be named as hydrogenation products according to Rule A-23

Examples to Rule A-53.3

See Recommendations'93 R-2.4.4

Rule A-54. Three or More Identical Ring Systems 

54.1 - Unbranched assemblies consisting of three or more identical hydrocarbon ring systems are named by placing an appropriate numerical prefix before the name of the hydrocarbon corresponding to the repetitive unit. The following numerical prefixes are used:

3. ter-	7. septi-
4. quater-	8. octi-
5. quinque-	9. novi-
6. sexi-	10. deci-

Example to Rule A-54.1

54.2 - Unprimed numbers are assigned to one of the terminal systems, the other systems being primed serially. Points of attachment are assigned the lowest numbers possible.

Examples to Rule A-54.2

54.3 - As exceptions, unbranched assemblies consisting of benzene rings are named by using the appropriate prefix with the radical name "phenyl".

Examples to Rule A-54.3

See Recommendations'93 R-2.4.4

Rule A-55. Radicals for Identical Ring Systems 

(Alternative in part to Rule A-56.1)55.1 - Univalent and multivalent radicals derived from assemblies of identical hydrocarbon ring systems are named by adding "-yl", "-ylene" or "-diyl", "-triyl", etc., to the name of the ring assembly.

Examples to Rule A-55.1

See Recommendations'93 R-2.4.4

Rule A-56. Radicals for Non-benzenoid Ring Systems 

(Alternative in part to Rule A-55.1)56.1 - Radicals derived from hydrocarbon ring assemblies other that benzene ring assemblies by removal of one or more hydrogen atoms from only one ring are named with that ring as the parent radical, the remaining rings being named as substituents.

Examples to Rule A-56.1

Note: This method is used for assemblies of non-identical systems; also it is sometimes preferable to that of Rule A-55 for assemblies of identical systems when a group to be specified as a suffix or as a separate word is present in a chain attached to the ring assembly.See Recommendations'93 R-2.4.4