Naming compounds substituents

Compounds of the form RN2 X are named by adding the suffix -diazonium to the name of the parent compound RH, the whole being followed by the name of X- (Rule C-931.1, e.g., methanediazonium tetrafluoroborate, benzenediazonium chloride, not phenyldiazonium). Following RC- 82.2.2.3 (IUPAC, 1993), diazonium ions may also be named structurally on the basis of the parent cation diazenylium HNJ, e.g., benzenediazenylium ion. We name the substituent — NJ diazonio (not diazonium) following the same rule. Diazonio describes both mesomeric structures — N = N and — N = N. If one wants to describe one of these structures only, diazyn-l-ium-l-yl or diazen-2-ylium-l-yl has to be used for -N = N or -N = N, respectively. In the General Subject Index of Chemical Abstracts and in Beilstein, diazonium compounds as a class are indexed under this heading. 

Halogens (F, Cl, Br, I) are usually not named in the suffix of a compound. They get named as substituents, which we will see later on. 

Halogens are named as substituents in the following way fluoro, chloro, bromo, and iodo. Essentially, we add the letter 0 at the end to say that they are substituents. If there are multiple substituents of the same kind (for example, if there are five chlorine atoms in fhe compound), we use fhe same prefixes fhaf we used earlier when classifying fhe number of double and friple bonds ... 

EXERCISE 5.28 In the following compound, identify all groups that would be considered substituents, and then indicate how you would name each substituent ... 

Systematic names describe the molecular structure of a compound. A systematic name consists of two parts, . The is the name of a compound having a particular caibon skeleton. The are a list of one or more radical groups connected by chemical bonds to the parent compound. Substituents are arranged in alphabetical order within a compound name. If the parent contains more than one carbon atom, each substiuent name is preceded by a number identifying the carbon atom in the parent compound to which it is connected. 

Most of the cardiotonic pyridazine derivatives discussed in the preceding chapter also exhibit vasodilator effects. In addition, various dihydropyrida-zine derivatives like (52), structurally closely related to calcium-antagonistic Hantzsch-type dihydroypyridines, have been patented as coronary vasodilators [169-171]. Another type of pyridazine analogue of the previously mentioned dihydropyridines, namely compounds of type (53), in which the aryl substituent at C-4 is represented by a pyridazine nucleus, has been claimed in a patent [172]. Quite recently, pyridazinyldihydropyridine-3,5-dicarboxyl-ates (54,55) have been prepared in Austria [173]. 

The foregoing examples illustrate that naming compounds from structures or deducing structures from names requires knowledge of both the parent names and the substituent names of the important types of functional and nonfunctional groups. This information is summarized in the following sections and Table 7-1. 

IUPAC - standard guidelines for naming compounds Nomenclature Strategy - find longest carbon chain, identify and note location of functional groups and substituents by chain position number. 

Structures and the recommended names of compounds belonging to the bomane group of bicyclic terpene hydrocarbons are given in Chart 14. Reasons for coining the name bornane and for the necessity of using the norbomane-type names to systematize the nomenclature of the bicyclo 2.2. [] heptane bicyclics have been presented earlier. Examination of the names in Chart 14 reveals that in the systematic bicyclo 2.2.1 ]heptane names and the recommended norbornane names the prefix numbers for substituents and double bonds and the order of names of substituents are identical. 

Allowing the addition of one carbon atom, or at most only two, to a terpene parent compound carbon skeleton for naming compounds as derivatives of that parent" (proposed by L. A. Goldblatt). This principle does not depend on a distinction between like and unlike groups, but is based merely on the number of carbon atoms in the substituents. Therefore, it allows such names as methylpinane, methylenepinane, (chlorometbyl)pinane, and (if two additional carbons are allowed) ethyl-pinane. The first of these four types of names are not allowed by either Proposal I or Proposal II. The other three types are allowed by I but not by II. 

Rule 4 Organizing Multiple Groups The final rule deals with naming compounds with more than one substituent. 

With all the different functional groups we have studied, it is not always obvious which functional group of a multifunctional compound is the main one and which groups should be named as substituents. In choosing the principal group for the root name, we use the following priorities ... 

Why do we use numbers for some descriptions such as 2,4-dibromophenol but also use ortho and para in others The numbers are best in naming compounds but we need ortho and para to describe the relationship between substituents. Phenol brominates n both ortho positions. In this molecule they happen to be positions 2 and 6 but in other molecules, where the OH group is not on Cl, they wiil have other numbers, but they will still be ortho to the OH group. Use whichever description suits the point you are making. 

Many organic compounds contain more than one functional group. When one of those functional groups is halo (X-) or alkoxy (RO-), these groups are named as substituents as described in Sections 7.2 and 9.3B. To name other polyfunctional compounds, we must learn which functional group is assigned a higher priority in the rules of nomenclature. Two steps are usually needed ... 

Figure 6.3.6 Naming compounds according to the position of the substituent...

The best performance of OLEDs based on V-shaped oligomers was obtained with the oxigenated compound frmctionalized with (3-cyclohexyl substituents, namely compound 11,... 

Names of the heterocyclic ring systems (whose syntheses are shown) are given under the formulae efforts have been made to ensure that, as far as possible, these comply with lUPAC recommendations, but it has not been possible to check every compound from recently published papers. As mentioned in Section I, the names are for the ring systems and do not include the names of substituents... 

The relative positions of two substituents on a benzene ring can be indicated either by numbers or by the prefixes ortho, meta, and para. Adjacent substituents are called ortho, substituents separated by one carbon are called meta, and substituents located opposite one another are designatedpara. Often, only their abbreviations (o, m,p) are used in naming compounds. 

Substitutive nomenclature (Section 4.3F) A system for naming compounds in which each atom or group, called a substituent, is cited as a prefix or suffix to a parent compound. In the lUPAC system only one group may be cited as a suffix. Locants (usually numbers) are used to tell where the group occurs. 

The suffix labels the functional group whose presence places the molecule into the appropriate class of chemical compounds. In this scheme the saturated hydrocarbons, the alkanes have the suffix -ane. For naming isomers, the system is more complicated and includes additional rules. Since the molecules of isomers are branched, the root name must correspond to the longest chain. The sidechains are treated as additional groups called substituents. In the final name of the structure, the substituents are introduced as prefixes to the root. The names of substituents are formed following the same rules as in the case of simple alkanes, i.e. the number of C-atoms followed by the suffix -yl. 

Number of C-atoms Formula Root Suffix Name of compound Substituent Suffix Name... 

Sometimes it is more convenient to name compounds if we view the benzene ring itself as a substituent. For example, the compound... 

Common names for alkynes are derived by prefixing the names of substituents on the carbon-carbon triple bond to the word acetylene. Note in the third example that when a carbon-carbon double bond (indicated by -en-) and a carbon-carbon triple bond (indicated by -yn-) are both present in the same molecule, the lUPAC rules specify that the location of fhe double bond takes precedence in numbering the compound. 

When three or more substituents are present on a ring, their locations are specified by numerals. If one of the substituents imparts a special name, then the compoimd is named as a derivative of that parent molecule. If none of the substituents imparts a special name, the substituents are numbered to give the smallest set of numbers and are listed in alphabetical order before the ending -benzene. In the following examples, the first compound is a derivative of toluene and the second is a derivative of phenol. Because there is no special name for the third compound, its three substituents are listed in alphabetical order and the atoms of the ring are numbered using the lowest possible set of numbers. 

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