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Principles of Organic Nomenclature

R-1.2.8 Multiplicative operation

R-1.2.8.1 Assemblies involving di- or polyvalent substituent groups. When a compound contains identical units whose only substituents are the principal characteristic groups, and when these identical units are linked by a symmetrical di- or polyvalent substituent group, it may be named by stating successively (a) the locants for the positions of substitution of the di- or polyvalent substituent group into the identical units, (b) the name of the di- or polyvalent substituent group, (c) the numerical prefix "di-" or "tri-", etc., and (d) the name of one of the identical units including the principal characteristic group. The numbering of the identical units and the principal characteristic group is retained, and when there is a further choice the points of substitution by the di- or polyvalent substituent group are numbered as low as possible. Primes, double primes, etc., are used to distinguish the locants of the identical units. If there is a choice, the greater number of primes is given to the locants of the unit having the higher numbered point of attachment to the di- pr polyvalent group.

Examples to R-1.2.8.1

R-1.2.8.2 Names of symmetrical di- or polyvalent substituent groups are formed by juxtaposing the names of the individual substituent groups starting with the central one, e.g., methylenedioxy, oxydiethylene; or the trivial name, if any, for compound substituent groups may be used.

Examples to R-1.2.8.2

(In the last example, the compound substituent group name is formed by starting with the central substituent group "oxy", followed by "-bis-", and adding successively the names of the substituent groups "ethylene" () and "nitrilo" (), and finally the name of the unit "propanoic acid", preceded by the multiplicative prefix "tetra").

Note: In this nomenclature operation, unsymmetrical compound substituent groups are not used for linking identical units because of difficulty in assigning an unambiguous numbering to the complete structure. Instead, simple substitutive nomenclature is used.

Example to R-1.2.8.2

R-1.2.8.3 Derivatives of assemblies of identical units. When assemblies names in accordance with R-1.2.8.1 contain substituents in the identical units in addition to the principal characteristic groups, these substituents are named by used of prefixes. These prefixes are assigned the lowest locants available after priority has been given to the principal characteristic groups and the linking di- or polyvalent substituent groups.

Examples to R-1.2.8.3

Note: Assemblies of identical units linked by di- or polyvalent substituent groups where the individual units contain different numbers of the principal group are named by simple substitutive nomenclature.

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This HTML reproduction is as close as possible to the published version [see IUPAC, Commission on Nomenclature of Organic Chemistry. A Guide to IUPAC Nomenclature of Organic Compounds (Recommendations 1993), 1993, Blackwell Scientific publications, Copyright 1993 IUPAC]. If you need to cite these rules please quote this reference as their source.

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