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Hydrocarbon Ring Assemblies

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

Non-identical Ring Systems
Three or More Identical Ring Systems
Radicals for Identical Ring Systems
Radicals for Non-benzenoid Ring Systems


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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