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.
52.2 - If there is a choice in numbering, unprimed numbers are assigned to the system which has the lower-numbered point of attachment.
Examples to Rule A-52.1
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.
Example to Rule A-52.2
52.4 - The name "biphenyl" is used for the assembly consisting of two benzene rings.
Examples to Rule A-52.3
See Recommendations'93 R-2.4.4
Examples to Rule A-52.4
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.
Published with permission of the IUPAC by Advanced Chemistry Development, Inc., www.acdlabs.com, +1(416)368-3435 tel, +1(416)368-5596 fax. For comments or suggestions please contact firstname.lastname@example.org