Nomenclature branching

A number of glossaries of terms and symbols used in the several branches of chemistry have been pubHshed. They include physical chemistry (102), physical—organic chemistry (103), and chemical terminology (other than nomenclature) treated in its entirety (104). lUPAC has also issued recommendations in the fields of analytical chemistry (105), coUoid and surface chemistry (106), ion exchange (107), and spectroscopy (108), among others. 

As we cover new functional groups in later chapters, the applicable IUPAC rules of nomenclature will be given. In addition, Appendix A at the back of this book gives an overall view of organic nomenclature and shows how compounds that contain more than one functional group are named. For the present, let s see how to name branched-chain alkanes and learn some general naming rules that are applicable to all compounds. 

Alkanes are a class of saturated hydrocarbons with the general formula C H2n. -2- They contain no functional groups, are relatively inert, and can be either straight-chain (normal) or branched. Alkanes are named by a series of IUPAC rules of nomenclature. Compounds that have the same chemical formula but different structures are called isomers. More specifically, compounds such as butane and isobutane, which differ in their connections between atoms, are called constitutional isomers. 

After such a revolution (in Kuhn s nomenclature), a period starts that he calls normal science . This means that the relevant field of science develops in a logical way by verification and falsification processes, but without fundamentally new discoveries. Kuhn showed that periods of normal science are based on paradigms. In classical Greek 7iapa5 vyna means a model, a shining example, but also admonition in the sense of a warning example. In science a paradigm may isolate a branch of science from new or potential developments. 

IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN), Nomenclature of branched-chain monosaccharides (Recommendations 1980), Eur. J. Biochem., 119, 5-8... 

The carbohydrate nomenclature jointly established by the American and British Committees4 does not specifically refer to the branched-chain sugars nevertheless, the application and extension of its Rules can provide definitive names to augment or to replace the trivial or unsystematic terms which have been conferred on naturally occurring, branched-chain sugars and related synthetic products, including the branched-chain saccharinic acids.6 9... 

A systematic nomenclature, besides correlating the above products, can remove the difficulties which have, in certain cases, been encountered on employing the trivial name of a branched-chain sugar in naming its derivatives. 7 9... 

A further complication that may be encountered in the nomenclature of branched-chain monosaccharides is in the numbering of the carbon atoms of the molecule. There is some precedent for numbering the carbon atoms of the branched moiety continuously with the carbon atoms of the main chain. However, this can result in confusion and ambiguity, especially when there are further substituents on the branched carbon atoms. In this connection, the Geneva system of nomenclature11 provides a reasonable solution, which is illustrated in the naming of compounds XII10 and XIII. 

Exposure Levels in Environmental Media. Reliable monitoring data for the levels of di- -octylphthalate in contaminated media at hazardous waste sites are needed so that the information obtained on levels of di-ra-octylphthalate in the environment can be used in combination with the known body burden of di-w-octylphthalate to assess the potential risk of adverse health effects in populations living in the vicinity of hazardous waste sites. Di-u-octylphthalate has been detected in ambient air, rain, surface water, groundwater, and sediment. However, as a result of the confusion about the nomenclature for octylphthalate esters, much of the historical monitoring data available actually pertain to the branched isomer, di(2-ethylhexyl)phthalate (Vista Chemical 1992). Therefore, little current information specific to the /1-octyl isomer is available regarding concentrations of the compound in foods, drinking water, and environmental media, particularly with respect to media at hazardous waste sites. The lack of monitoring data precludes the estimation of human exposure via intake of or contact with contaminated media. 

PTT is made by the melt polycondensation of PDO with either terephthalic acid or dimethyl terephthalate. The chemical structure is shown in Figure 11.1. It is also called 3GT in the polyester industry, with G and T standing for glycol and terephthalate, respectively. The number preceding G stands for the number of methylene units in the glycol moiety. In the literature, polypropylene terephthalate) (PPT) is also frequently encountered however, this nomenclature does not distinguish whether the glycol moiety is made from a branched 1,2-propanediol or a linear 1,3-propanediol. Another abbreviation sometimes used in the literature is PTMT, which could be confused with poly(tetramethylene terephthalate),... 

FIGURE 5.1 Cluster model of amylopectin. A and B denote nomenclature of branch chains, 0=reducing end, c.l. = chain length in degree of polymerization. Reprinted from Carbohydrate Research, Vol. 147, Hizukuri (1986), Polymodal distribution of the chain lengths of amylopectin, and its significance, Pages 342-347, with permission from Elsevier. 

It is also common and correct to name amines with each alkyl branch listed as an attachment before the suffix -amine. In this system of nomenclature, the molecules in Figure 1.16 are ethylamine, methyl ethyl amine, and methyl diethyl amine. Several other methods of naming amines exist, but they will not be covered in this course. 

Eur. J. Biochem. (1980) 111, 295-298 Nomenclature of unsaturated monosaccharides Eur. J. Biochem. (1981) 119, 1-3 Nomenclature of branched-chain monosaccharides Eur. J. Biochem. (1981) 119, 5-8 Abbreviated terminology of oligosaccharide chains /. Biol Chem. (1982) 257, 3347-3351 Polysaccharide nomenclature /. Biol Chem. (1982) 257, 3352-3354 Symbols for specifying the conformation of polysaccharide chains... 

J. Biol Chem. (1986) 261, 13-17 Nomenclature of junctions and branch points in nucleic acids... 

The polymer is commonoly referred to as poly(dimethylsiloxane), but the IUPAC name is either poly(oxydimethylsilanediyl) or catena-poly[(diphenylsilicon)-p-oxo] depending on whether one uses the nomenclature rules for organic or inorganic polymers. The prefix catena refers to a linear polymer, not branched or crosslinked. 

The names of inorganic and coordination polymers are based on the same fundamental principles that were developed for organic polymers. As in the nomenclature of organic polymers, these rules apply to structural representations that may at times be idealised and do not take into account irregularities, chain imperfections or random branching. 

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