Nomenclature Note No. 1

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

One of the goals of the Nomenclature Committee is to improve communication between polymer scientists by recommending unambiguous, standardized, and universally understood names and terms describing polymeric materials. The Committee and the Commission on Macromolecular Nomenclature of the International Union of Pure and Applied Chemistry (IUPAC) have embarked on projects leading to a more efficient dissemination of information on existing reports and recommendations on nomenclature and terminology related to polymer science and technology. One example is the publication in early 1991 of the IUPAC "Compendium of Macromolecular Nomenclature" (The Purple Book) by Blackwell Scientific Publications of Oxford, England.

Another project, to which this column is an introduction, is the insertion of a "Nomenclature Note" in each issue of the Polymer Preprints. Depending on the suggestions and feedback received, this column may provide highlights of some nomenclature and terminology recommendations, a limited tutorial on the nomenclature of special classes or types of polymers, answers to some questions of general interest, or reports on international polymer nomenclature developments. Although there exist two parallel polymer nomenclature systems, source-based and structure-based, each to be applied when appropriate, basically depending on the type and amount of information available, the two systems are often intermixed. What is also frustrating at times is the lack of correspondence between structural representations and the names which are to describe the structures.

Recently in a review article on conductive polymers the following set of names and structures was tabulated:

A quick inspection reveals that the first two names reflect the source-based nomenclature. "Pyrrole" and "thiophene" are starting materials or monomers. Yet, the structures shown, even if idealized, provide more information. Not only they show the bivalent constitutional repeating units, but also indicate ‚ as has been shown experimentally ‚ that heteroatomic nuclei are linked at the 2 and 5 positions. Would not then the structure-based names such as

"poly (2, 5-pyrrolediyl)" and "poly (2, 5-thienylene)"

be more informative?

On the other hand, the next two names are structure-based since the bivalent groups, "phenylene", "thienylene", and "vinylene" for

respectively, are correctly employed, except that again the linkage positions shown in the structures are not reflected in the names. Thus, the names corresponding to the structures should in fact be

"poly(1,4-phenylenevinylene)" and "poly(2,5-thienylenevinylene)"

It might be mentioned parenthetically that although "thienylene" has frequently been encountered in literature, the preferred IUPAC name is "thiophenediyl", formed in accordance with the general rule for a name of a bivalent group derived from a heterocycle.

The correct use of parentheses in the "poly" names is essential. In source-based names, the name of the monomer should be enclosed if it consists of more than one word, e.g., "poly(methyl methacrylate)".

In structure-based names, the constitutional repeating unit (CRU), also known as structural repeating unit (SRU), should always be enclosed in parentheses whether it consists of a single bivalent group or a combination of groups, e.g., "poly(2,5-pyrrolediyl)" and "poly(1,4-phenylenevinylene)".

The Nomenclature Committee is soliciting comments and suggestions on how to make this column most useful. Please address them, as well as any questions, to the Committee Chairman.

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