Conventions for Naming Chemicals

This chapter discusses lUPAC and CAS nomenclature systems and the SMILES notation, along with examples of each. Multiple names for a single well-defined substance—ethyl acrylate—are also presented. 

The official naming convention under REACH is that developed and maintained by lUPAC. The lUPAC system is intended to allow an experienced chemist to name a structure under the system by following a set of rules. In practice, many chemical substances are very complex and application of the rules requires the interpretation of a chemist who is an expert not just in chemistry, but also in lUPAC nomenclature. Some chemicals, for the purpose of the European Inventory of Existing Chemical Substances (EINECS) and REACH, have lUPAC names that are common names rather than names that follow a set of rules. lUPAC publishes new lists of names periodically, and occasionally a common name is replaced by a more formal one. This practice results in multiple names for the same substance, and the most current name is not necessarily the one originally placed onto EINECS. CAS offers a service by which it assigns a CAS name and CASRN for a substance for which one already knows the structure and/or the reactants used in the manufacture of the substance, but there is no direct counterpart to this process to identify a correct lUPAC name. There are indirect means such as by cross-checking against a known CAS name and CASRN, or other information such as the chemical s EINECS number. 

The systematic lUPAC system in its simplest form operates under a few basic principles. Application of these rules results in common names in simple cases that are familiar to students of inorganic and organic chemistry. Eor the purposes of this contribution, our focus will be on organic chemicals. The following is representative of lUPAC rules  

Use the name of the parent alkane, such as meth for a single carbon eth for two carbons and prop for three carbons, and the suffix ane for a straight-chain saturated carbon sequence the common names methane, ethane, and propane result. 

Cyclic structures very simply are named as the parent hydrocarbon prefixed by the term cyclo. For example, C4H8 

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In living organisms, chiral molecules are usually present in only one of their chiral forms. For example, the amino acids in proteins occur only as their l isomers glucose occurs only as its D isomer. (The conventions for naming stereoisomers of the amino acids are described in Chapter 3 those for sugars, in Chapter 7 the RS system, described above, is the most useful for some biomolecules.) In contrast, when a compound with an asymmetric carbon atom is chemically synthesized in the laboratory, the reaction usually pro-... 

Perhaps at this point you are feeling confused hy the many different conventions for naming different kinds of chemical compounds. Here is an overview of the guidelines for naming and writing formulas for all of the types of compounds descrihed in this chapter and in Chapter 3. 

Tables 1.1 and 1.2 show the most relevant organic and hybrid organic-inorganic molecules used throughout the body of the book in alphabetical order. The schemes of the molecules go hand in hand with their most commonly accepted acronyms as well as reduced chemical names. Instead of using the well-established International Union of Pure and Applied Chemistry (lUPAC) convention for unequivocally identifying the molecules, we follow a reduced formulation, thinking more of the non-chemist communities. For instance, 7,7,8,8-tetracyano-/ -quinodimethane will be simplified to tetracyano-quinodimethane and 2,3,6,7-tetramethyl-l,4,5,8-tetraselenafulvalene to tetramethyl-tetraselenaful-valene. In general the reduction will consist in removing the numeric locators. This modification should not affect the comprehension of the issues described in the hook. In case of douht it is recommended to consult the schemes in the mentioned tables. The molecules will be classified in the next sections...

Second, data can also occur as the value of an attribute to the element. In the example above, the element has two attributes, version= "l. 0" and convention "inchi". Both the name of the attribute and its value can be enumerated if needed by the schema if the attribute is unknown, or its value is outside defined limits, the entire document or datument can be flagged as invalid by suitable software. Thus has attributes elementType="C" and x2 = "-5.4753". For the former, a value of C is allowed (because it is recognized as the standard symbol for the chemical element carbon), but a value of say CX would not be allowed. The second attribute is defined (in the schema) as the x coordinate of a set of two-dimensional molecular coordinates. As such, its presence implies that it should be paired with a yi coordinate. One can specify in the... 

The use of proper chemical nomenclature is essential for effective scientific communication. More than one million new substances are reported each year, each of which must be identified clearly, unambiguously, and completely in the primary literature. Chemical compounds are named according to the rules established by the International Union of Pure and Applied Chemistry (IUPAC), the International Union of Biochemistry and Molecular Biology (IUBMB) [formerly the International Union of Biochemistry (IUB)], the Chemical Abstracts Service (CAS), the Committee on Nomenclature, Terminology, and Symbols of the American Chemical Society, and other authorities as appropriate. For more information on naming chemical compounds, refer to the bibliography in Chapter 18. This chapter gives the editorial conventions and style points for chemical compound names. 

This equilibrium hypothesis is, however, not necessarily valid for rapid chemical reactions. This brings us to the second way in which solvents can influence reaction rates, namely through dynamic or frictional effects. For broad-barrier reactions in strongly dipolar, slowly relaxing solvents, non-equilibrium solvation of the activated complex can occur and the solvent reorientation may also influence the reaction rate. In the case of slow solvent relaxation, significant dynamic contributions to the experimentally determined activation parameters, which are completely absent in conventional transition-state theory, can exist. In the extreme case, solvent reorientation becomes rate-limiting and the transition-state theory breaks down. In this situation, rate con-... 

Isoprene is the common name for the chemical compound 2-methylbuta-l,3-diene. Conventionally, all natural compounds built up from isoprene subunits, (Cj) , are denoted as terpenes, therefore terpenes are also denoted as isoprenoids. Terpenes cover most of the range of natural products about 55000 terpenes are known at present in the literature. In Nature, terpenes occur predominantly as hydrocarbons, alcohols, and their glycosides, ethers, aldehydes, ketones, carboxylic acids, and esters [103]. 

The next three chapters concern chemical nomenclature. One from Hull University deals with integration of structure-based systems and nomenclature. Janusz Wisniewski, in a popularly acclaimed presentation, demonstrated Beilstein s AUTONOM program at the conference and his chapter describes this microcomputer program for generating lUPAC names from structural input. Val Metanomski and Joy Merritt provided a poster on Chemical Abstracts Service conventions for macromolecules. 

In the Author Index the names of all the authors whose publications are abstracted in that Chemical Abstracts volume are listed. Moreover, the names of patentees, inventors, industrial companies, societies, committees, government authorities, institutions and research organizations are also included. The Chemical Abstracts Service has established rules and conventions for the spelling and transliteration of authors names. These conventions are explained in each Volume 1 of the Chemical Abstracts preceding the Author Index. 

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