Characteristic group

Socrates G 1994 Infrared Characteristic Group Frequencies Tables and Charts 2nd edn (Chichester Wiley)... 

Woodruff and co-workers introduced the expert system PAIRS [67], a program that is able to analyze IR spectra in the same manner as a spectroscopist would. Chalmers and co-workers [68] used an approach for automated interpretation of Fourier Transform Raman spectra of complex polymers. Andreev and Argirov developed the expert system EXPIRS [69] for the interpretation of IR spectra. EXPIRS provides a hierarchical organization of the characteristic groups that are recognized by peak detection in discrete ames. Penchev et al. [70] recently introduced a computer system that performs searches in spectral libraries and systematic analysis of mixture spectra. It is able to classify IR spectra with the aid of linear discriminant analysis, artificial neural networks, and the method of fe-nearest neighbors. 

Aminoazobenzene is a member of the large class of azo-compounds, all of which contain the characteristic grouping, C-N N-C. Azo-compounds are of considerable technical importance, as they are all coloured, and the majority possess considerable stability. They may be prepared by the following methods ... 

Table 1.8 Characteristic Groups Cited Only as Prefixes in Substitutive...

Substitutive Nomenclature. The first step is to determine the kind of characteristic (functional) group for use as the principal group of the parent compound. A characteristic group is a recognized combination of atoms that confers characteristic chemical properties on the molecule in which it occurs. Carbon-to-carbon unsaturation and heteroatoms in rings are considered nonfunctional for nomenclature purposes. 

In Table 1.8 are listed characteristic groups that are cited only as prefixes (never as suffixes) in substitutive nomenclature. The order of listing has no significance for nomenclature purposes. 

Systematic names formed by applying the principles of substitutive nomenclature are single words except for compounds named as acids. First one selects the parent compound, and thus the suffix, from the characteristic group listed earliest in Table 1.7. All remaining functional groups are handled as prefixes that precede, in alphabetical order, the parent name. Two examples may be helpful ... 

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. 

If the characteristic group occurs only in a chain that carries a cyclic substituent, the compound is named as an aliphatic compound into which the cyclic component is substituted a radical prefix is used to denote the cyclic component. This chain need not be the longest chain. 

If the characteristic group occurs in more than one carbon chain and the chains are not directly... 

TABLE 1.7 Characteristic Groups for Substitutive Nomenclature Continued)... 

If the characteristic group occurs only in one cyclic system, that system is chosen as the parent. 

If the characteristic group occurs in more than one cyclic system, that system is chosen as parent which (a) carries the largest number of the principal group or, failing to reach a decision, (b) is the senior ring system. 

If the characteristic group occurs both in a chain and in a cyclic system, the parent is that portion in which the principal group occurs in largest number. If the numbers are the same, that portion is chosen which is considered to be the most important or is the senior ring system. 

Characteristic groups named as suffix following the ranking order of Table 1.7... 

Prefixes that represent complete terminal characteristic groups are preferred to those representing only a portion of a given group. For example, for the prefix — C(=0)CH3, the name (formylmethyl) is preferred to (oxoethyl). 

Characteristic groups will now be treated briefly in order to expand the terse outline of substitutive nomenclature presented in Table 1.7. Alternative nomenclature will be indicated whenever desirable. 

Carboxylic acids —CO2H All types 3000-2500 as in tropolones OH stretching a characteristic group of small... 

G. Socrates, Infrared Characteristic Group Trequencies, 2nd ed., John Wiley Sons, Inc., New York, 1994. 

Substitution (see Seetion 1.02.9.1.1) is the formal proeedure most widely applied in modifying parent names. Indeed, the general term substitutive nomenclature is often used to describe the system of nomenclature in which substitution is the main operation. A fundamental concept of this system is that of the principal characteristic group . 

For nomenclature purposes, substituents can be divided into those that are always cited as prefixes (e.g. chloro-, alkoxy-) and those which can be cited as either prefixes or suffixes e.g. oxo-/-one, carbamoyl-/-carboxamide). If any of the latter are present, the name will normally contain a suffix. However, only one kind of group can be cited as suffix, and this is chosen according to a strict order of priorities. The group thus selected is known as the principal characteristic group . 

Since the characteristic grouping of the resins discussed in this chapter largely disappears on cross-linking it is difficult to make simple generalisations relating structure to properties. 

Peroxide class General structures or characteristic group... 

Sulfanuric halides contain the characteristic group -N=S(0)X- (X = Cl, F). Unlike the isoelectronic cyclophosphazenes (NPClajx (x = 3-17), " only six-membered rings have been well characterized. The sulfanuric halides are colourless solids (X = Cl) or liquids (X = F), which are stable in dry air. Sulfanuric chloride [NS(0)C1]3 is best prepared by treatment of SOCI2 with sodium azide in acetonitrile at -35°C (Eq. 8.16). It may also be obtained as a mixture of a- and yS-isomers in a two-stage reaction from H2NSO3H and PCls. The fluoride [NS(0)F]3 is formed as a mixture of isomers by the fluorination of [NS(0)C1]3 with Sbp3. ... 

The spectrum of a mixture of compounds is essentially that of the sum of the spectra of the individual components, provided association, dissociation, polymerisation, or compound formation does not take place. In order to detect an impurity in a substance, comparison can be made of the spectrum of the substance with that of the pure compound impurities will cause extra absorption bands to appear in the spectrum. The most favourable case will occur when the impurities present possess characteristic groupings not present in the main constituent. 

Compounds containing the neutral (formally zwitterionic) group =N2 attached by one atom to carbon are named by adding the prefix diazo- to the name of the parent compound (Rule 931.4), e.g., diazomethane, ethyl diazoacetate. Diazo is a so-called characteristic group appearing only as a prefix in substitutive nomenclature. Chemical Abstracts and Beilstein indexing of diazo compounds is analogous to that mentioned above for diazonium ions and salts, but Diazo compounds is not... 

The presence of certain absorption bands in visible and ultraviolet spectra can often be traced to the presence of characteristic groups of atoms in the molecules. These groups of atoms are called chromophores, front the Greek words for color bringer. ... 

What Are the Key Ideas The properties anti reactions of many organic compounds are due to the presence of characteristic groups of atoms known as functional groups. 

Socrates, G., Infrared and Raman Characteristic Group Erequencies, John Whey Sons, New York, 2004, 366. 

These results thus show that whereas the flashpoint was only moderately influenced by the compound structure (their chemical functionality but especially their atomic composition and vapour), autoignition temperatures seem to be closely linked to the structural factors that affect the chain. So additivity rules for estimation of AIT should be sought. Every time a chemical or physical property is highly influenced by the structure, chemists tried to establish rules that enable one to reduce a molecule to characteristic groups for which the contribution to the value of this property is known. This was done for instance by Kinney for boiling points and Benson2 for thermochemical properties. 

G. Socrates, Infrared and Raman characteristic group frequencies, John Wiley Sons LTD, Baffins Lane, Chichester, West Susses P019 lUD, England, 2001, p. 1-347. 

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