Heterocyclic compounds properties

The physical properties of a number of aliphatic ethers are collected in Table 111,60. Some related heterocyclic compounds are included in the Table. 

Since then, the fundamental physicochemical aspects of the synthesis and properties of ev anines have been exhaustively reviewed by Heseltine and Stunner in the fourth edition of Mee s treatise (3) and by Sturmer in Weissberger s edition of the Chemistry of Heterocyclic Compounds (4). So the purpose of this section dealing especially with thiazolomethine dyes is to give, apart from a complete and recent list of dyes and references, a description of the particularities of their chemistry and chiefly of the reaction mechanisms involved in their synthesis that have remained unknown or have not been discussed until now. 

D. Stunner, Syntheses and Properties of Cyanine and Related Dyes. The Chemistry of Heterocyclic Compounds. Wiley. New York. 1977. 

Table 13. Properties of Miscellaneous Fluorinated Heterocyclic Compounds...

Of interest, and occasional importance (in whiteness enhancers, for instance), are the fluorescent properties of heterocyclic compounds. Fluorescence is quite frequently found in the compounds relevant to this volume the acridines and acridones show it particularly often, but it appears in a number of very diverse systems. The fluorescence and phosphorescence of heterocyclic molecules have been reviewed by Schulman <74PMH(6)147). 

The importance of the penicillins as a class of heterocyclic compounds derives primarily from their effectiveness in the treatment of bacterial infections in mammals (especially humans). It has been estimated that, in 1980, the worldwide production of antibiotics was 25 000 tons and, of this, approximately 17 000 tons were penicillins (81MI51103). The Food and Drug Administration has estimated that, in 1979 in the U.S.A., 30.1 x 10 prescriptions of penicillin V and 44.3 x 10 prescriptions of ampicillin/amoxicillin were dispensed. This level of usage indicates that, compared to other methods of dealing with bacterial infection, the cost-benefit properties of penicillin therapy are particularly favorable. Stated differently, penicillin treatment leads to the elimination of the pathogen in a relatively high percentage of cases of bacterial infection at a relatively low cost to the patient in terms of toxic reactions and financial resources. 

The successful application of heterocyclic compounds in these and many other ways, and their appeal as materials in applied chemistry and in more fundamental and theoretical studies, stems from their very complexity this ensures a virtually limitless series of structurally novel compounds with a wide range of physical, chemical and biological properties, spanning a broad spectrum of reactivity and stability. Another consequence of their varied chemical reactivity, including the possible destruction of the heterocyclic ring, is their increasing use in the synthesis of specifically functionalized non-heterocyclic structures. 

Modern concepts have been extended to the chemistry of heterocyclic compounds more slowly than to the chemistry of aromatic and aliphatic systems, but efforts are now being made to classify and explain the properties and reactions of heterocyclic compounds in terms of these newer ideas (cf. reference 11). However, many of the most important heterocyclic compounds are potentially tautomeric, and elucidation of their tautomeric composition must precede a logical treatment of their properties. Further, many natural products such as the nucleic acids and alkaloids contain potentially tautomeric groups and information of this type is needed for a detailed explanation of th reactions which they undergo,... 

Other structures may be found in Reference 63. Physical properties of a limited number of heterocyclic compounds are given in Reference 49, p. 1003. 

We include here a short discussion of diazocyclopentadiene (4.21), its 2,3,4,5-tetra-cyano derivative (4.22), and the analogous heterocyclic compound 2-diazo-4,5-di-cyanoimidazole (4.23). Their synthesis and properties are discussed in Sections 2.6 and 12.2, where it is mentioned that they show in some respects the behavior of diazonium ions, i.e., of the mesomeric structure 4.21b (also analogously for 4.22 and 4.23). 

The Chemistry of Heterocyclic Compounds has been published since 1950 under the initial editorship of Arnold Weissberger, and later, until his death in 1984, under the joint editorship of Arnold Weissberger and Edward C. Taylor. In 1997, Peter Wipf joined Prof. Taylor as editor. This series attempts to make the extraordinarily complex and diverse held of heterocyclic chemistry as organized and readily accessible as possible. Each volume has traditionally dealt with syntheses, reactions, properties, structure, physical chemistry, and utility of compounds belonging to a specihc ring system or class (e.g., pyridines, thiophenes, pyrimidines, three-membered ring systems). This series has become the basic reference collection for information on heterocyclic compounds. 

N-heterocyclic compounds containing six-membered rings (pyridine and analogues) behave as excellent -acceptors and in turn they provide a rather soft site for metal ion coordination. The 7r-excessive five-membered pyrazole is a poorer 7r-acceptor and a better 7r-donor and it acts as relatively hard donor site. Inclusion of six- and five-membered N-heterocycles like pyridine and pyrazole in one ligand system leads to very attractive coordination chemistry with variations of the electronic properties.555 The insertion of a spacer (e.g., methylene groups) between two heterocycles, which breaks any electronic communication, makes the coordination properties even more manifold. 

In this article, a description has been given of recent investigations in the field of thiepin chemistry which are important for the major seven-membered unsaturated heterocyclic compounds. While the properties of these sulfur heterocycles have been determined quite well, some important questions still remain unexplored. Our current research efforts involve attempts to understand more generally the substituent effects on the thermal stability of the thiepin. 

Sturmer DM (1977) Syntheses and properties of cyanine and related dyes. In Weissberger A, Taylor EC (eds) The chemistry of heterocyclic compounds special topics in heterocyclic chemistry. Wiley, New York... 

Cyclic voltametric analysis has been utilized to determine material properties of this class of heterocyclic compounds. All the DTPs 23 <2003JOC2921 > exhibited a well-defined irreversible oxidation presumably corresponding to the formation of the radical cation. When scanned to higher positive potentials, it resulted in two consecutive broad oxidations for most of the DTPs. The second oxidation is quite weak, followed by a more intense and well-defined third oxidation. Coupling of thiophene radical cation is usually rapid (r <10-5 s) <1995SM(75)95>. These additional broad waves most likely correspond to the oxidation of coupled products rather than further DTP oxidations. The electrochemical data of the DTP S 23 are given in the Table 10. 

Chemical properties and structure of heterocycles containing P—C—O and P—C—N fragments are determined by the interaction between the heteroatoms. This interaction is most clearly pronounced in heterocyclic compounds also possessing an acceptor functional group (B(III), O—B(III), N—B(III), etc.). 

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