When rules are being compiled by the IUPAC Commission on Macromolecular Nomenclature, the activities of which this Committee fully supports, hypothetical examples are often used in order to illustrate all sorts of potential cases.

Once the rules are in place and they have been in use for some time, it might be useful to browse through the literature, select a number of actually synthesized and reported polymers, and apply the recommended nomenclature to them.

In this Note, we are reviewing four examples taken from the previous issue of Polymer Preprints in order to point out how more precise nomenclature does improve the description of the synthesized polymers by

(i) providing the necessary details, e.g., locants for substituents and linkages between the constituent repeating units;

(ii) bringing about the exact correspondence between the structure and the name.

This is well expressed in the new "Guide to IUPAC Organic Nomenclature":(3)

"The main purpose of chemical nomenclature is to identify a chemical species by means of written or spoken words. To be useful for communication among chemists, nomenclature for chemical compounds should additionally contain within itself an explicit or implied relationship to the structure of the compound, in order that the reader or listener can deduce the structure (and thus the identity) from the name. This purpose requires a system of principles and rules, the application of which gives rise to a systematic nomenclature."

1. A polyester prepared by the reaction of 2,6-naphthalenedicarbonyl dichloride with 1,4-butanediol(4) was named "poly(butylene 2,6-naphthalene) (PBN)" in analogy to the well known poly(ethylene terephthalate) (PET)" and "poly(butylene terephthalate) (PBT)". The two latter names do reflect the repeating units derived from the diol and diacid:

ethylene: -CH₂CH₂- or butylene: -CH₂CH₂CH₂CH₂-

and terephthalate (1,4-benzenedicarboxylate): -O-CO-p-C₆H₄-CO-O-

but "2,6-naphthalene" does not indicate two carboxylate groups. Thus, we recommend for this constitutional repeating unit (CRU) a trivial name and a structure-based name:

poly(butylene 2,6-naphthalenedicarboxylate)

poly(oxybutane-1,4-diyloxycarbonylnaphthalene-2,6-diylcarbonyl)

It might be noted that according to the most recent IUPAC recommendations for organic nomenclature,(3) the locants for the bivalent groups such as "1,4-" and "2,6-" are placed immediately before that part of the name to which they relate, that is, to indicate the locants for the bonds linking the constituent units.

2. A polyester containing oligothiophenes was synthesized by the reaction of a bis(2-hydroxyethyl) derivative of quaterthiophene with succinyl dichloride:(5)

the systematic name of which is

poly[(3,3'''-dimethoxy[2,2':5',2'':5'',2'''-quaterthiophene]-5,5'''-diyl)-
thioethyleneoxysuccinyloxyethylenethio]

The constitutional (structural) repeating unit has been rearranged according to the IUPAC recommendations to start citing from left to right the most senior subunit, which in this case is the assembly of four heterocycles. The name accurately reflects the location of each bond between the successive constituent units.

3. An azidomethyl group-containing polyurethane was synthesized by the reaction of sodium azide with a bromomethyl group-containing polymer:(6)

the systematic name of which is

poly[oxy[2,2-bis(azidomethyl)propane-1,3-diyl]oxycarbonyliminohexane-1,6-diyliminocarbonyl]

Conforming to the IUPAC recommendations, "propanediyl" and "hexanediyl" are used in preference to "trimethylene" and "hexamethylene", respectively, and ‚ as pointed out for the first example above ‚ the locants "1,3-" and "1,6-" immediately precede the suffixes "diyl" to which they relate.

4. An irregular polyester containing sequences of units derived from 1,1'-binaphthyl-4,4'-diol (BND) and 2,6-naphthalenedicarboxylic acid (NDA), and from 6-hydroxy-2-naphthoic acid (HNA)(7) is best represented by showing the repeating units not connected to each other to avoid an implication that these are block sequences, since the authors clearly state that "6-oxy-2-naphthoate" units have a random distribution:

the structure-based name of which is

poly(oxy[1,1'-binaphthyl]-4,4'-diyloxycarbonylnaphthalene-2,6-diylcarbonyl/oxynaphthalene-2,6-diylcarbonyl) (70:30 mole %)

It is worth noting that

a. the oblique stroke inserted between the constitutional units indicates the irregular sequential arrangements of these units;

b. the dashes at the end of each such unit are drawn fully inside the enclosing marks, because they do not necessarily denote terminal bonds of the macromolecule;

c. if the ratio of units is known then it should be expressed in numerical values in parentheses after the structural formula or the name, but not next to the parentheses in the fomula.

REFERENCES

1.Polym. Prepr. 1991, 32(1), 655-656; 1992, 33(2), 6-7; 1994, 35(1), 6-9; 1995, 36(1), 6-9.
2.a. IUPAC. "Compendium of Macromolecular Nomenclature" (The Purple Book). Blackwell Scientific Publications, Oxford, 1991; available in the U.S. from CRC Press, Boca Raton, Florida.
b. IUPAC. "Nomenclature of Regular Single-Strand Organic Polymers". Pure Appl. Chem. 1976, 48, 373-385. Reprinted as Chapter 5 in Ref. 2a.
c. IUPAC. "Nomenclature of Regular Double-Strand (Ladder and Spiro) Organic Polymers". Pure Appl. Chem. 1993, 65, 1561-1580.
d. IUPAC. "Structure-Based Nomenclature for Irregular Single-Strand Organic Polymers". Pure Appl. Chem. 1994, 66, 873-889.
e. IUPAC. "Graphic Representations (Chemical Formulae) of Macromolecules". Pure Appl. Chem. 1994, 66, 2469-2482.
3.IUPAC. "A Guide to IUPAC Nomenclature of Organic Compounds". Blackwell Scientific Publications, Oxford, 1993.
4.Wilson, P.; Brittain, W. J. Polym. Prepr. 1995, 36(2), 136.
5.5. Miller, L. L.; Hong, Y. Ibid. 75.
6.Sandberg, M. O.; Sano, M.; Yoshimura, S. Ibid. 93.
7.Bhowmik, P. K.; Atkins, E. D. T.; Han, H. Ibid. 326.


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*Chemical Abstracts Service, P.O. Box 3012, Columbus, OH 43210.