Structure-based nomenclature

For regular organic polymers that have only one species of constitutional repeating unit (CRU) in a single sequential arrangement and consist of single strands, the name is of the form poly(CRU). 

The CRU is named as an organic divalent group according to the usual rules for organic chemistry. The steps involved are identification of the unit orientation of the unit and naming of the unit. 

To obtain a unique name, a single preferred CRU must be selected. Therefore, rules have been developed that specify both seniority among subunits, that is, the point at which to begin writing the CRU, and also the direction in which to move along the chain to reach the end of the CRU. 

The order of seniority among the types of divalent group is  

Within each structural type, the seniority is dictated by the seniority of individual constituents. Examples of some of the rules are given below  

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The principles of structure-based nomenclature lUPAC nomenclature... 

Two systems of polymer nomenclature have been introduced - the source-based and the structure-based. The latter cannot be used for all types of macromolecule, e.g., statistieal copolymer molecules and polymer networks. lUPAC expresses no strong preference for the use of structure-based nomenclature versus source-based nomenclature, but for certain purposes one system of naming may be preferred to the other.. ... 

Structure-based nomenclature is based on a method of naming the sequence of constitutional or structural units that represent the repeating pattern of the structure of a typical macromolecule in a polymer. The name bears no direct relation to the structure of the (co)monomer(s) used to synthesize the polymer. 

The structure-based nomenclature rests upon the selection of a preferred CRU [1, 12] of which the polymer is a multiple the name of the polymer is the name of this repeating unit prefixed by poly . The unit itself is named wherever possible according to the established principles of organic nomenclature [3]. For double-strand polymers, this unit usually is a tetravalent group denoting attachment to four atoms. Since some of these attachments may be double bonds, the unit may be hexavalent or octavalent. Table 6 lists some examples. 

Table 6. Examples of structure-based nomenclature for regular double-strand (ladder and spiro) organic polymers...

The rules of structure-based nomenclature of regular single-strand organic polymers are of fundamental importance in polymer nomenclature. The names of other kinds of polymers such as double-strand [7] and irregular polymers [8] are based on the principles given in this Report. 

The Commission acknowledges the first structure-based nomenclature rules for organic ladder and spiro polymers proposed by the Nomenclature Committee of the Division of Polymer Chemistry of the American Chemical Society [9]. 

American Chemical Society. A structure-based nomenclature for linear polymers , Macromolecules 1, 193-198 (1968). 

Structure-Based Nomenclature for Irregular Single-Strand Organic Polymers... 

As a general rule, chemical formulae for macromolecules should be written only in those cases where the structures of the constitutional units are known. A given structure may, however, be written in various ways to emphasize specific structural features such alternative structures need not necessarily reflect the order of citation dictated by structure-based nomenclature [2]. 

Application of this system should not discourage the use of structure-based nomenclature whenever the copolymer structure is fully known and is amenable to treatment by the rules for single-strand polymers [1, 2]. It is intended that the present nomenclature system supersede the previous recommendations published in 1952 [3]. 

Alternating sequence arrangements can form constitutionally regular structures and may, in those cases, also be named utilizing the structure-based nomenclature for regular single-strand organic polymers. The example above would be then named... 

Structure-based nomenclature for irregular single-strand organic polymers (lUPAC Recommendations 1994), Pure Appl. Chem. 66, 873-889 (1994). Reprinted as Chapter 17, this edition. 

Because the exact structure of the polymer is not always known, two systems of macromolecular nomenclature have been developed source-based nomenclature and structure-based nomenclature. 

Polynuclear compounds may be either of such large extended structures as to make rational structure-based nomenclature impractical, or the structures may be undefined or partially elucidated. In these instances compositional nomenclature is most suited. 

A Macromolecular Division of IUPAC was created in 1967, and it created a permanent Commission on Macromolecular Nomenclature, parallel to the other nomenclature commissions. The Commission over the years has issued recommendations on basic definitions, stereochemical definitions and notations, structure-based nomenclature for regular singlestrand organic polymers and regular single-strand and quasi-singlc-strand inorganic and coordination polymers, source-based nomenclature for polymers and abbreviations for polymers. All of these are collected in a compendium referred to as the IUPAC Purple Book. 

This was just one of the reasons why a more mathematically based system was developed. Unlike source-based nomenclature which merely attached the prefix poly to the name of some real or assumed monomer (the source), "structure-based" nomenclature analyzes the structure of a repeating unit in a molecule and selects as the desired "monomer" the smallest unit that consistently repeated in the aggregation. 

When assigning canonical names to moieties which fit the above limitation of a polymer, one especially focuses on the repeating unit in a structure-based nomenclature, and biases the organization according to dimension. For the completely general cases, one has ... 

The names given to the polymers in the following table exemplify elementary aspects of nomenclature. Thus source-based nomenclature places the prefix poly before the name of the monomer, the monomer s name being contained within parentheses unless it is a simple single word. In structure-based nomenclature the prefix poly is followed in parentheses by words which describe the chemical structure of the repeat unit. 

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