Transformations nomenclature

The major significance of chemical nomenclature or notation systems is that they denote compounds in order to reproduce and transfer them from one coding to another, according to the intended application. As each coding may not include all the pieces of information in the other coding, or may have interpre table coding rules, the transformation is not always unambiguous and unique. 

A nomenclature or notation is called unambiguous if it produces only one structure. However, the structure could be expressed in this nomenclature or notation by more than one representation, all producing the same structure. Moreover, uniqueness" demands that the transformation results in only one - unique -structure or nomenclature, respectively, in both directions. 

While the trivial and trade nomenclature in most cases has accidental character, the lUPAC Commission has worked out a series of rules [4] which allow the great majority of structures to be represented uniformly, though there still exists some ambiguity within this nomenclature. Thus, many structures can have more than one name. It is important that the rules of some dialects of the lUPAC systematic nomenclature are transformed into a program code. Thus, programs for generating the names from chemical structures, and vice versa (structures from names) have been created [5] (see Chapter II, Section 2 in the Handbook). 

Although the literature refers to the formation of chromones/coumarins as the Kostanecki reaction (and often the Kostanecki-Robinson reaction) and the synthesis of flavones as the Allan-Robinson reaction, others have chosen to merge the two reactions and refer to both transformations as the Kostanecki-Robinson reaction. This section will follow the latter school of thought, and use the Kostanecki-Robinson (K-R) nomenclature. 

In the present nomenclature to be called the diazonio group . In the IUPAC nomenclature for transformations this process is called diazonio-de-hydrogenation , or, in short, diazoniation . 

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 cyclic hemiacetal and hemiketal forms of monosaccharides are capable of reacting with an alcohol to form acetals and ketals (see Section 7.2). The acetal or ketal product is termed a glycoside, and the non-carbohydrate portion is referred to as an aglycone. In the nomenclature of glycosides we replace the suffix -ose in the sugar with -oside. Simple glycosides may be synthesized by treating an alcoholic solution of the monosaccharide with an acidic catalyst, but the reaction mixture usually then contains a mixture of products. This is an accepted problem with many carbohydrate reactions it is often difficult to carry out selective transformations because of their multifunctional nature. 

R. A. Y. Jones and J. F. Bunnett. Nomenclature for organic chemical transformations (lUPAC Recommendations 1989) , PureAppl. Chem. 61, 725-768 (1989). lUPAC. Compendium of Chemical Terminology, 2nd ed. (the Gold Book ). Compiled by A. D. McNaught and A.Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version http //goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata updates compiled by A. Jenkins. 

Replacement nomenclature is used to name heteromonocycles that contain more than ten atoms. In developing a replacement name, carbon atoms are regarded as exchanged for heteroatoms. The non-detachable prefixes (Table 4.8) are used to indicate the exchange. Cycloalkane or annulene names are the bases for transformation into the name of a heterocycle. 

Systematic substitutive nomenclature may be used to name all organic molecules. However, those that are of animal or vegetable origin have often received trivial names, such as cholesterol, oxytocin and glucose. Biochemical nomenclature is based upon such trivial names, which are either substitutively modified in accordance with the principles, rules and conventions described in Chapter 4, Section 4.5 (p. 70), or transformed and simplified into names of stereoparent hydrides, i.e. parent hydrides of a specific stereochemistry. These names are then modified by the rules of substitutive nomenclature. Three classes of compound will be discussed here to illustrate the basic approach carbohydrates amino acids and peptides and lipids. For details, see Biochemical Nomenclature and Related Documents, 2nd Edition, Portland Press, London (1992). 

The Diels-Alder reaction is one of the most important carbon-carbon bond forming reactions,521 522 which is particularly useful in the synthesis of natural products. Examples of practical significance of the cycloaddition of hydrocarbons, however, are also known. Discovered in 1928 by Diels and Alder,523 it is a reaction between a conjugated diene and a dienophile (alkene, alkyne) to form a six-membered carbo-cyclic ring. The Diels-Alder reaction is a reversible, thermally allowed pericyclic transformation or, according to the Woodward-Hoffmann nomenclature,524 a [4 + 2]-cycloaddition. The prototype reaction is the transformation between 1,3-butadiene and ethylene to give cyclohexene ... 

It is convenient to label the relative slowness of encounter pair reaction as due to an activated process and to remark that the chemical reaction (proton, electron or energy transfer, bond fission or formation) can be activation-limited. This is an unsatisfactory nomenclature for several reasons. Diffusion of molecules in solution not only involves a random walk, but oscillations of the molecules in solvent cages. Between each solvent cage in which the molecule oscillates, a transformation from one state to another occurs by passage over an activation barrier. Indeed, diffusion is activated (see Sect. 6.9), with a typical activation energy 8—12 kJ mol-1. By contrast, the chemical reaction of a pair of radicals is often not activated (Pilling [35]), or rather the entropy of activation... 

At temperatures above 250°C, the olefin-forming reactions are irreversible but the transformations in the first line of Scheme 3 are reversible. Thus, starting with an arbitrary amine, all other derivatives are obtained by these reactions, called disproportionations, transalkylations or dismutations (the nomenclature is also inconsistent in that the analoguous formation of ethers from alcohols is named dehydration). 

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