Addition compounds, nomenclature

A. Werner 13 regards thet rihalides as addition compounds, so that the trihalide RIC12 becomes [C1.I.C1JR, dichloriodates on his system of nomenclature. The pentahalides are tetrachloroiodates analogous to the chloroauriotes ... 

Naming becomes more difficult if the molecular complexity of a compound changes when it is fused or vaporized. Aluminum chloride is an ionic solid but vaporizes to dimeric molecules the solid is then aluminum trichloride whereas the vapor is dialuminum hexachloride. Similar considerations hold also for FeCl3, P2O5, and a number of additional compounds. Likewise, phosphorus(V) chloride is an appropriate name for PCI5 in the vapor state, but an ideal system of nomenclature should find some way of indicating that the solid consists of equal quantities of PCl and PClJf ions. It is a little difficult to decide just how much information about the structure of a compound must be included in its name before this name is to be considered adequate. 

Addition Reaction. The double bond of dehydroalanine and e-methyl dehydroalanine formed by the e-elimination reaction (Equation 6) is very reactive with nucleophiles in the solution. These may be added nucleophiles such as sulfite (44). sulfide (42), cysteine and other sulfhydryl compounds (20,47), amines such as a-N-acetyl lysine (47 ) or ammonia (48). Or the nucleophiles may be contributed by the side chains of amino acid residues, such as lysine, cysteine, histidine or tryptophan, in the protein undergoing reaction in alkaline solution. Some of these reactions are shown in Figure 1. Friedman (38) has postulated a number of additional compounds, including stereo-isomers for those shown in Figure 1, as well as those compounds formed from the reaction of B-methyldehydroalanine (from 6 elimination of threonine). He has also suggested a systematic nomenclature for these new amino acid derivatives (38). As pointed out by Friedman the stereochemistry can be complicated because of the number of asymmetric carbon atoms (two to three depending on derivative) possible. 

Others arise from the use of the registry system to support the preparation of index nomenclature. Thus, all parent ring systems are registered even when the parent compound has not been made. Also, all components of addition compounds, mixmres, or copolymers are registered and, occasionally, one of these components may not have been reported in the literamre. 

Nomenclature before Werner (to 1897)- The Lavoisierian system of nomenclature, even with the Berzelius modifications, provided no suitable names for that class of compounds which later was designated coordination compounds. Names based on the patterns for double salts and addition compounds were not satisfactory because the properties of these materials were not those consistent with the patterns provided. Consequently, names based on properties, especially color (Table I), or the names of prominent investigators became popular (2) because they, at least, did not commit the user to any theory of their structure. The developments in organic chemistry after 1860 did not contribute to the understanding of these strange compounds, so there was no carry-over to them of the nomenclature developments in organic chemistry. 

IR-1.5.3.2 Compositional nomenclature IR-1.5.3.3 Substitutive nomenclature IR-1.5.3.4 Additive nomenclature IR-1.5.3.5 General naming procedures IR-1.6 Changes to previous IUPAC recommendations IR-1.6.1 Names of cations IR-1.6.2 Names of anions IR-1.6.3 The element sequence of Table VI IR-1.6.4 Names of anionic ligands in (formal) coordination entities IR-1.6.5 Formulae for (formal) coordination entities IR-1.6.6 Additive names of polynuclear entities IR-1.6.7 Names of inorganic acids IR-1.6.8 Addition compounds IR-1.6.9 Miscellaneous... 

Compositional names are either of the stoichiometric type (which, furthermore, are of the binary type except in the case of homoatomic species) or of the addition compound type. Compositional nomenclature is used if little or no structural information is to be conveyed... 

Additionally, the nomenclature of cyclopeptide alkaloids has been kept unaltered by using the trivial names. The nomenclature proposed in (45) and (46), although chemically correct, is confusing especially when correlations or references to known compounds are made. Furthermore, since the present review article is centered on structure elucidation, some simplifications were adopted. Thus, in order to facilitate references or correlations with known compounds, the prefixes N- and 0-desmethyl or N- and (9-methyl have been used. 

The systematic lUPAC nomenclature of compounds tries to characterize compounds by a unique name. The names are quite often not as compact as the trivial names, which are short and simple to memorize. In fact, the lUPAC name can be quite long and cumbersome. This is one reason why trivial names are still heavily used today. The basic aim of the lUPAC nomenclature is to describe particular parts of the structure (fi agments) in a systematic manner, with special expressions from a vocabulary of terms. Therefore, the systematic nomenclature can be, and is, used in database systems such as the Chemical Abstracts Service (see Section 5.4) as index for chemical structures. However, this notation does not directly allow the extraction of additional information about the molecule, such as bond orders or molecular weight. 

Line notations represent the structure of chemical compounds as a linear sequence of letters and numbers. The lUPAC nomenclature represents such a kind of line notation. However, the lUPAC nomenclature [6] makes it difficult to obtain additional information on the structure of a compound directly from its name (see Section 2.2). 

The commercial 2D structure editor. Chemistry 4D-Draw, from Chemlnnovativc Software Inc., includes two additional special modules besides conventional chemical drawing tools. NamExpert provides the interpretation ofa compound name according to the lUPAC nomenclature to create the corresponding chemical structure. The latter can be represented in three different styles the shorthand. Kckulc. or semi-structural formula. In contrast to NamExpert, the Nomenclature module assigns lUPAC names to drawn structures. 

There are several types of nomenclature systems that are recognized. Which type to use is sometimes obvious from the nature of the compound. Substitutive nomenclature, in general, is preferred because of its broad applicability, but radicofunctional, additive, and replacement nomenclature systems are convenient in certain situations. 

For purely alicyclic compounds, the selection process proceeds successively until a decision is reached (a) the maximum number of substituents corresponding to the characteristic group cited earliest in Table 1.7, (b) the maximum number of double and triple bonds considered together, (c) the maximum length of the chain, and (d) the maximum number of double bonds. Additional criteria, if needed for complicated compounds, are given in the lUPAC nomenclature rules. 

Addition nomenclature, 1, 37 Addition reactions heterocyclic compounds reviews, 1, 70 Additives... 

It is possible to regard radicofunctional nomenclature, in which the functional class narrie of a compound (c.g. alcohol, ketone, etc.) is cited after the names of the attached radicals, as involving an additive procedure (example 146). This type of nomenclature is gradually falling out of use in favor of the substitutive equivalent [for 146 the substitutive name would be l-(3-pyridyl)propan-l-one]. 

Another type of anion, confined for practical purposes to boron compounds, has no unshared electrons at the anionic site, and must be thought of as being formed by addition of hydride to a boron atom (or other atom with an incomplete valence shell). Such structures were not anticipated at the time general heterocyclic nomenclature was developed, and they are only recently being fitted into systematic nomenclature (lUPAC Provisional Recommendation 83.2). Proposals for a suffix to indicate such structures are under consideration (1982). 

It should be stated that the nomenclature of the triazine derivatives is not uniform, e.g., in Chemical Abstracts the compounds are often indexed according to another sy.stem than that used in the original papers, and an additional system could have been used for this review. To avoid further complications, the author will u.se the commonest nomeclature in accordance with the representative monographs in this field (see references 12 and 45.)... 

The vocabulary in this edition contains an estimated total of 59,000 terms, some of the larger additions being in the fields of chemical technology, electronics, and warfare. Additional meanings are given for many terms that were listed in the earher editions, The latest decisions in nomenclature are followed in particular, the Stock valence names for inorganic compounds are freely given, as well as the older names. 

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. 

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