IUPAC naming system

A newer IUPAC naming system places the number locant of the double bond immediately before the -ene suffix (not used in this book). 

Following this system, the IUPAC names of the isomers of pentane are... 

Alcohols containing two hydroxyl groups are commonly called gylcols. In IUPAC substitutive system they are named as diols. 

Chemical identity may appear to present a trivial problem, but most chemicals have several names, and subtle differences between isomers (e.g., cis and trans) may be ignored. The most commonly accepted identifiers are the IUPAC name and the Chemical Abstracts System (CAS) number. More recently, methods have been sought of expressing the structure in line notation form so that computer entry of a series of symbols can be used to define a three-dimensional structure. For environmental purposes the SMILES (Simplified Molecular Identification and Line Entry System, Anderson et al. 1987) is favored, but the Wismesser Line Notation is also quite widely used. 

In addition, other systems of nomenclature for AHLs have also appeared in the literature describing them as derivatives of furanone, y-butyrolactone or 4-butanolide. For example, the above V.fischeri autoinducer can also be named as (S)-N-(3-oxohexanoyl)-3-aminodihydro-2(3H)-furanone,(S)-a-(3-oxohexa-noyl)amino-y-butyrolactone or (S)-2-(3-oxohexanoyl)amino-4-butanolide (another IUPAC name) [27]. 

In the IUPAC system locants are placed immediately before the part of the name to which they apply for instance subunits such as pyridine-2,4-diyl and l-methylpropane-l,3-diyl. One of the few exceptions is the phenylene subunit, for example, 1,4-phenylene in XV. The IUPAC nomenclature system is always evolving and some of the details (e.g., the names of some subunits) have changed in recent years. One should use caution when using less recent nomenclature references than those listed in this text. 

The IUPAC nomenclature system recognizes that most of the common (commercial) polymers have source-based or semisystematic names that are well established by usage. IPUAC does not intend that such names be supplanted by the IUPAC names but anticipates that such names will be kept to a minimum. The IUPAC system is generally used for all except the common polymers. The IUPAC names for various of the common polymers are indicated below the more established source or semisystematic name in the following ... 

Name each of the polymers in Problem 1-1 by the IUPAC system. Indicate alternate names where applicable based on the polymer source, non-IUPAC structure system, or trade names. 

Lactams are named in several ways. They are named as alkanolactams by the IUPAC substitutive system, such as 3-propanolactam, 4-butanolactam, 5-pentanolactam, and 6-hexano-lactam, respectively, for the 4-, 5-, 6-, and 7-membered rings, respectively. An alternate IUPAC method, the specialist heterocyclic nomenclature system, names these lactams as 2-azetidinone, 2-pyrrolidinone, 2-piperidinone, and hexahydro-2f/-azepi n-2-one, respectively. These lactams are also known by the trivial names fl-propiolactam, a-pyrrolidone (y-butyrolactam), a-piperidone (8-valerolactam), and e-caprolactam, respectively. 

For a useful classification of strained polycyclic systems, see Gund Gund J. Am. Chem. Soc. 1981, 103, 4458. " For a computer program that generates IUPAC names for complex bridged systems, sec Rucker Rucker Chimia 1990, 44, 116. 

In the reaction sections of this book, we shall give IUPAC names for most transformations (these names will be printed in the same typeface used above), including examples of all eight types.3 As will become apparent, some transformations require more rules than we have given here.2 However, it is hoped that the simplicity of the system will also be apparent. 

In the third edition I included the new IUPAC names for organic transformations. Since then the rules have been broadened to cover additional cases hence more such names are given in this edition. Furthermore, IUPAC has now published a new system for designating reaction mechanisms (see p. 290), and I now include some of the simpler of these new designations. 

We will base our study on the system developed by the International Union of Pure and Applied Chemistry. The system is called the IUPAC Rules. There are other semi-systematic nomenclature systems, and many individual compounds are known by nonsystematic or trivial names. These names will be given along with the IUPAC names when such trivial names are commonly used. 

The IUPAC rules assign names to unbranched alkanes as shown in Table 2.2. Methane, ethane, propane, and butane are retained for CH4, CH3CH3, CH3CH2CH3, and CH3CH2CH2CH3, respectively. Thereafter, the number of carbon atoms in the chain is specified by a Latin or Greek prefix preceding the suffix -ane, which identifies the compound as a member of the alkane family. Notice that the prefix n- is not part of the IUPAC system. The IUPAC name for CH3CH2CH2CH3 is butane, not n-butane. 

The IUPAC rules are not the only nomenclature system in use today. Chemical Abstracts Service surveys all the world s leading scientific journals that publish papers relating to chemistry and publishes brief abstracts of those papers. The publication Chemical Abstracts and its indexes are absolutely essential to the practice of chemistry. For many years Chemical Abstracts nomenclature was very similar to IUPAC nomenclature, but the tremendous explosion of chemical knowledge has required Chemical Abstracts to modify its nomenclature so that its indexes are better adapted to computerized searching. This means that whenever feasible, a compound has a single Chemical Abstracts name. Unfortunately, this Chemical Abstracts name may be different from any of the several IUPAC names. In general, it is easier to make the mental connection between a chemical structure and its IUPAC name than its Chemical Abstracts name. 

Ethylene is an acceptable synonym for ethene in the IUPAC system. Propylene, isobutylene, and other common names ending in -ylene are not acceptable IUPAC names. 

Cyclic compounds that contain at least one atom other than carbon within their ring are called heterocyclic compounds, and those that possess aromatic stability are called heterocyclic aromatic compounds. Some representative heterocyclic aromatic compounds are pyridine, pyrrole, furan, and thiophene. The structures and the IUPAC numbering system used in naming their derivatives are shown. In their stability and chemical behavior, all these compounds resemble benzene more than they resemble alkenes. 

Ethylene glycol and propylene glycol are common names for these two diols and are acceptable IUPAC names. Aside from these two compounds, the IUPAC system does not use the word glycol for naming diols. 

The nomenclature (qv) of polyamides is fraught with a variety of systematic, semisystematic, and common naming systems used variously by different sources. In North America the common practice is to call type AB or type AABB polyamides nylon-x or nylon-x,x, respectively, where x refers to the number of carbon atoms between the amide nitrogens. For type AABB polyamides, the number of carbon atoms in the diamine is indicated first, followed by the number of carbon atoms in the diacid. For example, the polyamide formed from 6-aminohexanoic acid [60-32-2] is named nylon-6 [25038-54-4] that formed from 1,6-hexanediamine [124-09-4] or hexamethylenediamine and dodecanedioic acid [693-23-2] is called nylon-6,12 [24936-74-1]. In Europe, the common practice is to use the designation "polyamide," often abbreviated PA, instead of "nylon" in the name. Thus, the two examples above become PA-6 and PA-6,12, respectively. PA is the International Union of Pure and Applied Chemistry (IUPAC) accepted abbreviation for polyamides. 

The International Union of Pure and Applied Chemistry (IUPAC) adopted a system that is clear. For noncyclic alkanes, the root gives the number of carbons in the longest chain. Each branch is described by a prefix indicating the number of carbons in the branch, and a number indicating the point of connection to the longest chain. (Numbering starts at the end of the chain which produces the smallest numerals.) The IUPAC names for the structures above are butane and 2-methyl propane. ... 

Aldehydes, acids, and esters have roots for one and two carbons that are usually form- and acet-, rather than meth- and eth-, because these prefixes had been used so long they were grandfathered into the naming system (formaldehyde and acetic acid, rather than methanal and ethanoic acid). Departures from IUPAC nomenclature often occur for very common substances and, fortunately, they rarely can be misunderstood (ethyl alcohol instead of ethanol). 

The compound which is customarily called p-xylylene or p-quinodimethane is denoted as 1,4-dimethylene-2,5-cyclohexadiene under the IUPAC nomenclature system. However, since in this review article reference is frequently made to the orginal papers, the trivial names are retained. 

Fig. 20 IUPAC Name Dichloro[N,N-dimethyl-2,2 -thiobis(ethylamine)-S,N ]platinum(II) Systemic Name PtlSl( l)2Nl (U)(lCf) 3[1(C1)2N1C1H 7(1C1H)]...

IUPAC common name IUPAC alternate name Systemic name... 

Note that because of the use of beta bonds, rather than fixed single and double bonds, there is not inconsistency between the molecule depicted and the common vs. the alternate IUPAC names. The double bonds are NOT localized, as the IUPAC picture implies. To the contrary, 5H-Pyrrole is, because of symmetry just another (non-canonical) name for 2H-Pyrrole. Additionally, one should note that a 3H-Pyrrole can also be formed. This would have as its systemic name NP(CP)4 (1H). 

---