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|Tous les auteurs / collaborateurs :||
Zory V Todres
|ISBN :||9781420066074 1420066072|
|Numéro OCLC :||154804593|
|Description :||xix, 290 pages : illustrations ; 24 cm|
|Contenu :||Ch. 1. Oxadiazoles --
ch. 2. Thiadiazoles --
ch. 3. Selenadiazoles --
ch. 4. Telluradiazoles --
ch. 5. Chalcogenadiazoles from the standpoint of isosterism.
|Responsabilité :||Zory Vlad Todres.|
|Plus d’informations :|
"Preface This book considers the chemical, biomedical, and technical importance of chalcogenadiazoles. These compounds contain five-membered cycles composed of two carbons, two nitrogens, and one chalcogen--the latter as the key heteroatom. Chalcogens are chemical elements of VIA group of the periodic system, namely, oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and polonium (Po). At present, all chalcogenadiazoles are known naturally except for the polonium species. The external shells of the O, S, Se, and Te atoms have s2p4 configuration. These elements are isovalent. As the atomic number increases, covalent and ionic radii increase, and ionization energies decrease. At first glance, some similarities between analogously constructed chalcogenadiazoles might be expected. At a narrower glance, the fundamental properties of the key atoms in chalcogenadiazoles vary significantly, and these differences can lead to disparities between the molecules under consideration. The number of different chalcogenadiazoles and their structural diversity make it difficult to gain a good understanding of the subject by studying an individual class of these hetrocycles. The book tries to identify and emphasize general features of this family of heterocycles. The combined presence of the mentioned atoms endows heterocyclic systems with some specific properties. The book concentrates on properties of each class of chalcogenadiazoles and their cycle-fused derivatives, considering chemical reactions of functional groups only in cases when these properties permit to characterize the heterocycles as substituents or in respect of its aromaticity. Nitrogen-oxides and chalcogen-oxides of these heterocycles are equally discussed"--