Heterocyclic nitrogen compounds basic

Heptane-4,6-dione, decafluoro-metal complexes decomposition, 385 Heptane-2,4,6-trione metal complexes, 399 Heteroallenes coordinated reactivity, 579 metal complexes, 579 Heterocyclic nitrogen compounds basic pKa... 

With heteroaromatic substrates it is possible to prepare, for example, thiazolyipyridines. It is noteworthy that basic solvents (e.g., heterocyclic nitrogen compounds) increase the yield of substitution by a cage effect (see Tables III-37 and III-38) (208). 

Poisoning occurs by strong adsorption of stable molecules on the active sites of catalysts. Basic heterocyclic nitrogen compounds can usually poison the acidic sites. Adsorption of... 

CAS 91-22-5. C9H7N. A basic heterocyclic nitrogenous compound occurring in coal tar and obtained from it, but more frequently by synthesis. 

Chemistry provides a definition of alkaloids in purely chemical terms. Chemists stress that alkaloids are any group of complex heterocyclic nitrogen compounds, which have strong physiological activity, are often toxic, and retain their own basic chemical properties. It is also stated that there are a few exceptions to this definition.Another chemical definition states only that alkaloids are nitrogen-containing compounds derived from plants and animals. Later, chemists stressed that alkaloids were bio-... 

Halogenide complexes of heavy metals such as mercury bismuth, cadmium and antimony can be used in the titration of some basic heterocyclic nitrogen compounds < and among others, thiamineS > In this latter example, thiamine was titrated... 

In addition, liver preparations from rats induced with Aroclor 1254 (Monsanto) showed the best general applicability for activation. However, individual differences in effectiveness do occure.g., in the results given in Table 5, variously induced preparations show obvious differences between fraction 9 (the basic fraction. Be) and fraction 14 (the neutral/methanol fraction). The Aroclor-induced preparation works best with the neutral fraction (PAHs ), whereas the phenobarbital-induced preparations work more efficiently with the basic fraction (heterocyclic nitrogen compounds, aromatic amines, aza-arenes ). 

Spectroscopic evidence indicates that protonation of 2-fluoro-and 2-chloro-quinoline is not appreciable in O.OlJf aqueous hydrochloric acid. Protonation becomes evident in more strongly acidic solution in the case of the chloro compound without any accompanying decomposition, but the fluoro compound hydrolyzes to carbostyril under the latter conditions. The hydrolysis is acid-catalyzed, but it is doubtful whether protonation on the heterocyclic nitrogen is responsible, owing to its low basicity (presumably below that for the chloro compound). An alternative explanation in this case would be hydrogen bond formation with fluorine, Ar—F. .. H-O+H2. 

Methylation of nitrogen at the 2 position also proves to be consistent with diuretic activity. Condensation of 160 with urea affords the heterocycle, 193. Treatment of this compound with methyl iodide and base effects alkylation on the more acidic ring nitrogen (194). Basic hydrolysis then gives the N-methylated aminosulfonamide (195). Condensation of this with chloroacetalde-... 

Our discussions of the basicity of organic nitrogen compounds have concentrated predominantly on simple amines in which the nitrogen atom under consideration is part of an acyclic molecule. Many biologically important compounds, and especially drug molecules, are based upon systems in which nitrogen is part of a heterocycle. We shall consider the... 

These compounds exist as the amino tautomers and normally the imino forms are not observed. All react with acids at the heterocyclic nitrogen atom, giving salts. The protonated forms of both 2- and 4-aminoquino-lines are resonance hybrids (Scheme 3.10), but 4-aminoquinoline is more basic than 2-aminoquinoline, possibly because the nitrogen atoms that carry the charge between them in the corresponding cation are more widely separated. 

The basic monomers of nucleic acids are nucleotides which are made up of heterocyclic nitrogen-containing compounds, purines and pyrimidines, linked to pentose sugars. There are two types of nucleic acids and these can be distinguished on the basis of the sugar moiety of the molecule, Ribonucleic acids (RNA) contain ribose, while deoxyribonucleic acid (DNA) contains deoxyribose. The bases cytosine (C) adenine (A) and guanine (G) are common in both RNA and DNA. However, RNA molecules contain a unique base, uracil (U), while the unique DNA base is thymidine (T). These differences in the base structure markedly affect the secondary structures of these polymers. The structures of DNA and RNA are outlined in Appendix 5.2. 

Of special interest are compounds such as 3-hydroxyquinoline (11) for which it is expected that the heterocyclic nitrogen becomes more basic in the excited state whereas the hydroxyl group should become more acidic. 

A second factor which obviously plays a role in the adsorption of molecules on the hydrogenation sites is the Jt electron density. This factor was considered to be predominant in the study of Moreau et al. [10]. The role of the x electrons can explain the fact that, in the study of Nagai et al [53], cyclohexylamine and piperidine did not fit the linear correlation between the adsorption coefficient and the gas phase basicity the adsorption coefficient of these saturated nitrogen compounds was about twice lower than expected on the basis of the above mentioned correlation. In our experiments, the high adsorption coefficient of the pyrrolic ring can be related to the very high n character of this heterocycle [59]. 

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