Macromolecular Nomenclature Note No. 8

W. V. Metanomski *
Nomenclature Committee
ACS Division of Polymer Chemistry, Inc


Chemical Abstracts Service (CAS) last year assigned the 13 millionth CAS Registry Number, 155827-99-9, to a polymer, represented as a regularly repeating structural (constitutional) unit, as was reported in the October 1994 issue of the Divisional Newsletter on page 6:

(C39H16F18N4O6)n

Poly[(1,3-dihydro-1,3-dioxo-2H-isoindole-2,5-diyl)[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene] (1,3-dihydro-1,3-diazo-2H-isoindole-5,2-diyl)-1,3-phenyleneimino (2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-1,8-dioxo-1,8-octanediyl)imino-1,3-phenylene]

It is a synthetic polymer, a novel poly(amide imide) containing oligomeric segments of tetrafluoroethylene, reported in a paper on "Influence of flexible oligo(tetrafluoroethene) segments on the glass temperature of poly(aramide)s and poly(amide imide)s" by H. A. Schneider, N. Steinhauser, and R. Mulhaupt of the University of Freiburg, published in Polym. Bull. (Berlin) 1994, 32, 339-346, and abstracted in CA 1994, 121, 10424x.

In this Macromolecular Nomenclature Note, we will use this as an example to illustrate how the name of polymer is derived, based on both the source and the structure.

SOURCE-BASED NOMENCLATURE

The polymer was obtained by polycondensation of "2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride" with "m-benzenediamine containing tri(tetrafluoroethene) segments". The two starting materials or monomers were:

2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride and

N,N'-(dodecafluorooctanedioyl)bis(m-benzenediamine)

According to the IUPAC recommendations on "Source-Based Nomenclature for Copolymers",(1) the name of the copolymer is constructed by citing the names of the constituent monomers after the prefix "poly", and by placing between the names of each pair of monomers an italicized connective denoting the kind of the sequence arrangement, if known.

Thus, the name of the copolymer is:

poly[[2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride]-alt-[N,N'-(dodecafluorooctanedioyl)bis(m-benzenediamine)]]

The recommendations allow the use of trivial, semi-systematic, or systematic names, as long as these names are unambiguous and fully describe the substance. The order of citation of monomers is arbitrary. The connective "-alt-" indicates the alternating arrangement of monomeric units derived from starting reactants.

CAS, on the other hand, registers, indexes, and names polymers on the basis of monomers by using systematic CA Index names(2) and conforming to the requirements of alphabetically arranged "inverted" names in the CA Chemical Substance Index. Thus, we find there the monomer-based index entries for the polymer illustrated above:

1,3-Isobenzofurandione, 5,5'-[2,2,2-trifluoro-l-(trifluoromethyl)ethylidene]bis-, polymer with N,N'-bis(3-aminophenyl)-2,2,3,3,4,4,5,5,6,6,7,7-dodecafluorooctanediamide

Octanediamide, N,N'-bis(3-aminophenyl)-2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-, polymer with 5,5'-(2,2,2-trifluoro-l-(trifluoromethyl)-ethylidene]bis[1,3-isobenzofurandione]

STRUCTURE-BASED NOMENCLATURE

According to the IUPAC recommendations on "Nomenclature of Regular Single-Strand Organic Polymers",(3) which are based on the seminal ACS recommendations from 1968,(4) the polymer is named as "poly(constitutional repeating unit)", wherein the repeating unit is named as a bivalent organic group according to the usual nomenclature rules for organic chemistry. The steps involved in naming are: (1) identification of the unit; (2) orientation of the unit; and (3) naming of the unit. It is useful to draw first a larger segment of the chain containing two or more repeating units:

The repeating unit is readily identified and there are a number of them, as shown by brackets of different size. To arrive at a unique name, a preferred unit must be selected. This is done by selecting a bivalent subunit of the highest seniority and proceeding to the subunit of the same seniority, or to the subunit next in seniority, by the shortest path.

For citation of the first subunit, the order of seniority among the types of bivalent groups is: (1) heterocycle; (2) acyclic hetero atom; (3) carbocycle; and (4) chain containing carbon atoms only.

A quick inspection of the structural drawing above shows that there are two identical heterocycles, isoindole derivatives, hence the citation from left to right must start with one of them:

In which direction to go is decided by finding the shorter part between those two heterocycles, which obviously is the single disubstituted carbon atom:

Because the combination of other subunits (carbocycle, nitrogen atom, and the eight-carbon chain) is symmetrical with respect to the first part of the repeating unit, the citation progresses then through the carbocycle, the nitrogen atom, the carbon chain, etc., till the end of the unit:

which is the structural representation shown and named on the first page.


REFERENCES

1.IUPAC. "Source-Based Nomenclature for Copolymers". Pure Appl. Chem. 1985, 57, 1427-1440. Reprinted as Chapter 7 in "Compendium of Macromolecular Nomenclature" (The Purple Book). Blackwell Scientific Publications, Oxford, 1991; available in the U.S. from CRC Press, Boca Raton, Florida.
2.CAS. "Chemical Substance Index Names" (Appendix IV) in CA Index Guide. Chemical Abstracts Service, Columbus, Ohio, 1994.
3.IUPAC. "Nomenclature of Regular Single-Strand Organic Polymers" Pure Appl. Chem. 1976, 48, 373-385. Reprinted as Chapter 5 in "Compendium".
4.ACS. "A Structure-Based Nomenclature for Linear Polymers". Macromolecules 1968, 1, 193-198.


___________
* Mailing address: Chemical Abstracts Service, P.O. Box 3012, Columbus, Ohio 43210-0012.