IUPAC substitutive

IUPAC substitutive nomenclature locants, prefixes, parent compound, and one suffix. 

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

IUPAC substitutive names are used for more complicated ethers and for compounds with more than one ether linkage. 

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. 

As usual, R is a hydrocarbon group or, in the simplest case, a hydrogen atom. The acidic hydrogen atom is the one bonded to oxygen. The IUPAC name of a carboxylic add can be obtained by substituting the suffix -oic acid for the final e in the name of the corresponding alkane. In practice, such names are seldom used. For example, the first two members of the series are commonly referred to as formic add and acetic add. 

IUPAC recommendations suggest that a copolymer structure, in this case poly(methyl methacrylate-co-styrene) or copoly(methyl methacrylate/slyrene), should be represented as 1. The most substituted carbon of the configurational repeat unit should appear first. This same rule would apply to the copolymer segments shown in Section 7.1. However, as was mentioned in Chapter I, in this book, because of the focus on mechanism, we have adopted the more traditional depiction 2 which follows more readily from the polymerization mechanism. 

In the Chemical Abstracts method (also accepted by IUPAC Rule C-912), the naming of monoazo compounds with radicals R derived from two identical parent hydrocarbon hydrides is the same as mentioned above (for an exception see C-912.2). If the azo group links groups that are different when unsubstituted (R-N2-R ), a parent molecule RH is treated as substituted by R -N2- (Rule C-912.4) thus, 1.8 is called 4-(2-hydroxy-l-naphthylazo)benzenesulfonic acid or 4-(2-hydroxy-... 

Since diazoates can be considered to be derived from oximes by substitution of nitrogen for the methine group, Hantzsch (1894) put forward the hypothesis that configurational isomerism was also occurring here. He therefore represented the isomeric diazoates by the structures 7.1 and 7.2, assigning the syn structure (7.1) to the labile diazoate and the anti (7.2) to the stable isomer. Nowadays the description recommended by IUPAC (1979) for such configurational isomers, namely (Z) instead of syn and (E) instead of anti, should be used. 

Dediazoniation refers to all those reactions of diazo and diazonium compounds in which an N2 molecule is one of the products. The designation of the entering group precedes the term dediazoniation, e. g., azido-de-diazoniation for the substitution of the diazonio group by an azido group, or aryl-de-diazoniation for a Gomberg-Bachmann reaction. The IUPAC system says nothing about the mechanism of a reaction (see Sec. 1.2). For example, the first of the two dediazoniations mentioned is a heterolytic substitution, whereas the second is a homolytic substitution. 

In this chapter the sections are arranged in accordance with the nomenclature of substitution transformations introduced by IUPAC (1989 c). In some sections homolytic and heterolytic dediazoniations are discussed together, provided that the diazo-nio group can be replaced by a specific group or class of groups homolytically as well as heterolytically. 

The replacement of an electrofugic atom or group at a nucleophilic carbon atom by a diazonium ion is called an azo coupling reaction. By far the most important type of such reactions is that with aromatic coupling components, which was discovered by Griess in 1861 (see Sec. 1.1). It is a typical electrophilic aromatic substitution, called an arylazo-de-hydrogenation in the systematic IUPAC nomenclature (IUPAC 1989c, see Sec. 1.2). 

It is of course possible to name individual radialenes according to IUPAC rules [e.g. per(methylene)cycloalkanes 1-4]. However, the descriptiveness of the term radialene may some day pave its way into the official nomenclature. For substituted [ ]radialenes we have proposed1 a pragmatic numbering system, in which an inner ring is numbered first, followed by an outer ring . The numbering of substituents should follow IUPAC rules. Thus, the hydrocarbon 7 is 4,4-diethyl-5,5-dimethyl[3]radialene, the ester 8 should be called 7-methoxycarbonyl-5,5-dimethyl[4]radialene, the nitrile 9 which can exist in four diastereomeric forms is (6Z,7Z)-6-cyano-5,5,7-trimethyl[4]radialene and the difunctionalized [5]radialene 10 is (7 ,6Z)-7-bromo-6-formyl-6-methyl[5]radialene. 

When the two radicals attached to the azo group are derived from different parent molecules, the IUPAC system places the term azo between the complete names of the (substituted) parent molecules (Rule C-911.2). This system resembles an older numbered azo bridge system. The Chemical Abstracts system names the compound as a parent molecule RH substituted by a radical R N=N— (Rule C-912.4). This system is particularly convenient for unsymmetrically substituted aliphatic azo compounds. 

The variety of methods of naming azo compounds which has been in use for many years may lead to considerable confusion, especially when attempts are made to name structural formulas of highly substituted dye molecules with several azo linkages. Furthermore, in regard to the older dye literature, an intuitive interpretation of an author s intention frequently seems more productive than a detailed analysis of the system of nomenclature which he may be using. An effort is made in this chapter to conform to either the IUPAC or the Chemical Abstracts system [la]. 

In an unsymmetrically substituted compound, the position of the azoxy oxygen must be specified. The IUPAC [2] rules are as follows ... 

Sn2 stands for substitution nucleophilic bimolecular. The IUPAC designation (p. 290) is AnDn. In this mechanism there is backside attack the nucleophile approaches the substrate from a position 180° away from the leaving group. The reaction is a one-step process with no intermediate (see, however, pp. 297-298 and 305). The C—Y bond is formed as the C—X bond is broken ... 

The SeI mechanism (substitution electrophilic unimolecular) is rare, being found only in certain cases in which carbon is the leaving atom (see 1-38, 1-39) or when a very strong base is present (see 1-1, 1-11, and 1-42).29 It consists of two steps with an intermediate carbanion. The IUPAC designation is DE + AE. 

This is called the SrnI mechanism,38 and many other examples are known (see 3-4, 3-5, 3-7,3-14). The IUPAC designation is T + DN + AN.39 Note that the last step of the mechanism produces Arl radical ions, so the process is a chain mechanism40 (see p. 678). An electron donor is required to initiate the reaction. In the case above it was solvated electrons from KNH) in NH,. Evidence was that the addition of potassium metal (a good producer of solvated electrons in ammonia) completely suppresssed the cine substitution. Further evidence for the SrnI mechanism was that addition of radical scavengers (which would suppress a free-radical mechanism) led to 8 9 ratios much closer to 1.46 1. Numerous other observations of SrnI mechanisms that were stimulated by solvated electrons and inhibited by radical scavengers have also been recorded.41 Further evidence for the SrnI mechanism in the case above was that some 1,2,4-trimethylbenzene was found among the products. This could easily be formed by abstraction by Ar of H from the solvent NH3. Besides initiation... 

In a reaction with a moderately long chain, much more of the product will be produced by abstraction (4) than by coupling (5). Cleavage steps like (2) have been called SHl (H for homolytic), and abstraction steps like (3) and (4) have been called Sh2 reactions can be classified as ShI or Sh2 on the basis of whether RX is converted to R by (2) or (3).9 Most chain substitution mechanisms follow the pattern (3), (4), (3), (4). . . . Chains are long and reactions go well where both (3) and (4) are energetically favored (no worse that slightly endothermic, see pp. 683, 693). The IUPAC designation of a chain reaction that follows the pattern (3), (4). . . is ArDR + ARDr (R stands for radical). 

This mechanism is the same as the simple electrophilic one shown on p. 734 except that the charges are reversed (IUPAC AN + AE or AN + AH). When the olefin contains a good leaving group (as defined for nucleophilic substitution), substitution is a side reaction (this is nucleophilic substitution at a vinylic substrate, see p. 335). 

It was mentioned above that even alkanes undergo Wagner-Meerwein rearrangements if treated with Lewis acids and a small amount of initiator. An interesting application of this reaction is the conversion of tricyclic molecules to adamantane and its derivatives.89 It has been found that all tricyclic alkanes containing 10 carbons are converted to adamantane by treatment with a Lewis acid such as AIC13. If the substrate contains more than 10 carbons, alkyl-substituted adamantanes are produced. The IUPAC name for these reactions is Schleyer adamantization. Some examples are... 

Aldersley, J. W., and M. Gordon Polyaddition and polycondensation-substitution effects in polycondensation systems. IUPAC Symposium on Macromolecular Chemistry, Prague 1965. Preprint p. 584. 

Unfortunately, a completely systematic method of naming aromatic compounds is not in use. The system used is a combination of trivial names and the IUPAC system. Sometimes- compounds that contain benzene rings are considered to be substituted benzenes, in which case the word benzene appears in the name of the compound along with the name of the substituent. 

The IUPAC rules name branched alkanes as substituted derivatives of the unbranched alkanes listed in Table 2.2. Consider the C H isomer represented by the structure... 

The IUPAC rules permit alkyl halides to be named in two different ways, called functional class nomenclature and substitutive nomenclature. In functional class nomenclature the alkyl group and the halide (fluoride, chloride, bromide, or iodide) are designated as separate words. The alkyl group is named on the basis of its longest continuous chain beginning at the carbon to which the halogen is attached. 

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