Identification of heterocyclic

Gas-liquid chromatography has been widely used for the identification of reaction mixtures and for the separation of heterocycles. Some typical conditions are shown in Table 34. 

Identification of the product(s) resulting from the reaction of heterocyclic compounds with diazomethane has been used in attempts to elucidate their tautomeric composition (for summaries, see references 7 and 41). This work was based on the assumption that if a compound which is capable of existing in both an —NH and an —OH form produced only the =NMe derivative when it w as treated with diazomethane, it existed entirely in the =NH form. On the other hand, formation of the —OMe derivative was interpreted to mean that a finite amount of the compound existed in the —OH form. In some cases the tautomer present in the solid state w as concluded to be different from that present in solution for example, 41 42 gave a higher proportion of the 3,4-dimethoxy derivative when ethereal diaz-... 

P Dugo, L. Mondello, E. Sebastian , R. Ottana, G. Eirante and G. Dugo, Identification of minor oxygen heterocyclic compounds of citi us essential oils by liquid chromatography-atmospheric pressure chemical ionisation mass specti ometiy , J. Liq. Chromatogr. 22 2991-3005 (1999). 

Infrared absorption spectra of heteropyrans have been used mainly for the identification of functional groups. Assignments of the bands belonging to heterocyclic bond vibrations (C=C, C—S, C—Se, C—Te) have not been common. As a rule, 4W-heteropyrans exhibit maxima at higher wave numbers than 2//-isomers. Typical IR absorption maxima for heteropyrans are shown in Table X. 

Tables 15 and 16 show the absorption maxima of some metal complexes of benzothiazolyl-substituted formazans 230 and 231.283 The wavelengths are metal ion dependent, making formazans useful reagents for the identification of specific metal ions or the simultaneous determination of two ions. The wavelengths are much longer than those of the formazan anion (Table 14). The general trend for electron-rich substituents is toward a larger shift this is to be expected as it tends to enhance the aromatic character of the ring and increase the covalent character of the metal — nitrogen bond. The sharpness of the absorption band has been attributed to coordination to the heterocyclic nitrogen as in 232.57S...

For the purpose of polymer/additive analysis most applications refer to vulcanisate analysis. Weber [370] has determined various vulcanisation accelerators (Vulkazit Thiuram/Pextra N/Merkapto/AZ/DM) in rubbers using PC. Similarly, Zijp [371] has described application of PC for identification of various vulcanisation accelerator classes (guanidines, dithiocarbaminates, thiuramsulfides, mercapto-substituted heterocyclic compounds, thioureas, etc.). The same author has also... 

Tabakovic, I. Anodic Synthesis of Heterocyclic Compounds. 185, 87-140 (1997). Takahashi, Y. Identification of Structural Similarity of Organic Molecules. 174, 105-134... 

Table 16.5 General structure of a sulfa drug, structure of five sulfa drugs containing six-mem-bered heterocyclic R substituents, and measured pK values pK values were calculated using a spectrophotometric titration. Errors represent the 95% confidence levels and both the values and the associated errors were obtained from fits of the data using Scientist for Windows. Reprinted with permission from Boreen AL, Arnold WA, McNeil K (2005) Triplet-sensitized photodegradation of sulfa drugs containing six-membered heterocyclic groups identification of an S02 extrusion photoproduct. Environ Sci Technol 39 3630-3638. Copyright 2005 American Chemical Society...

Stick RV (1997) The Synthesis of Novel Enzyme Inhibitors and Their Use in Defining the Active Sites of Glycan Hydrolases. 187 187-213 Stutz AE, see de Raadt A (1997) 187 157-186 Stumpe R, see Kim JI (1990) 157 129-180 Suami T (1990) Chemistry of Pseudo-sugars. 154 257-283 Suppan P (1992) The Marcus Inverted Region. 153 95-130 Suzuki N (1990) Radiometric Determination of Trace Elements. 157 35-56 Tabakovic I (1997) Anodic Synthesis of Heterocyclic Compounds. 185 87-140 Takahashi Y (1995) Identification of Structural Similarity of Organic Molecules. 174 105-134 Tasi G, Palinkd I (1995) Using Molecular Electrostatic Potentid Maps for Similarity Studies. 174 45-72... 

S., WaUing, T., Wild, H. (2001) Discovery of heterocyclic ureas as a new class of raf kinase inhibitors identification of a second generation lead by a combinatorial chemistry approach. Bioorg Med Chem Lett 11, 2775-2778. 

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