Nitrogen structure

True alkaloids derive from amino acid and they share a heterocyclic ring with nitrogen. These alkaloids are highly reactive substances with biological activity even in low doses. All true alkaloids have a bitter taste and appear as a white solid, with the exception of nicotine which has a brown liquid. True alkaloids form water-soluble salts. Moreover, most of them are well-defined crystalline substances which unite with acids to form salts. True alkaloids may occur in plants (1) in the free state, (2) as salts and (3) as N-oxides. These alkaloids occur in a limited number of species and families, and are those compounds in which decarboxylated amino acids are condensed with a non-nitrogenous structural moiety. The primary precursors of true alkaloids are such amino acids as L-ornithine, L-lysine, L-phenylalanine/L-tyrosine, L-tryptophan and L-histidine . Examples of true alkaloids include such biologically active alkaloids as cocaine, quinine, dopamine, morphine and usambarensine (Figure 4). A fuller list of examples appears in Table 1. 

The polymerization of butadiene to 1.2 polymers with anionic Ziegler type catalysts has been studied by Natta and co-workers (46). They have shown that isotactic 1.2-polybutadiene can be produced by the use of catalysts which are made up of components which have basic oxygen and nitrogen structures such as triethylaluminum with cobalt acetylacetonate or with chromium acetylacetonate. Natta and co-workers have shown that either syndiotactic or isotactic structures are produced depending on the ratio of aluminum to chromium. Syndiotactic structures are obtained at low aluminum to chromium ratios while isotactic polybutadiene is obtained at high ratios. The basic catalyst component is characteristic of syndiotactic catalysts. Natta, Porri, Zanini and Fiore (47) have also produced 1.2 polybutadiene using... 

Knicker H., Hatcher P. G., and Scaroni A. W. (1996) A solid-state NMR spectroscopic investigation of the origin of nitrogen structures in coal. Int. J. Coal Geol. 32, 255-278. 

Accordingly, more ammonia is released from easily decomposed aliphatic nitrogen structures than from more stable aromatic stmctures. 

Thermal decomposition temperature corrected relative intensities (%) of nitrogen structures ... 

Nitrogen content in aquatic humic materials usually ranges from 0.5 to 2%, although in seawater DOM it has been reported to be as high as 6.5% (Thurman and Malcolm, 1989). Little is known about the nature of the combined nitrogenous structural types that are present, although hydrolytic studies have revealed some bound amino acids (Lytle and Perdue, 1981 Thurman and Malcolm, 1989). 

Mullins OC. Sulfur and nitrogen structures in asphaltenes and related materials quantified by Xanes spectroscopy. In Sheu EY, Mullins OC, editors. Asphaltenes Fundamentals and applications. New York Plenum Press 1995. p 53-96. 

Although both commercially successful cationic HEC derivatives (27 and 28) are based on the hydroxyethylcellulose backbone, because of their unique quaternary nitrogen structures, they have found different niches in the personal care industry. Cationic HEC, 27, more commonly known by its International Nomenclature Cosmetic Ingredient (INCI) name, polyquaternium-10, is used as a conditioner delivered from shampoo and conditioner formulations. The cationic HEC, 28, known by its INCI name, polyquaternium-4, is found as a conditioning and fixative adjuvant in hair fixative formulations such as mousses. 

Mehandjiev, D.R. Nickolov, R.N.. and loncheva. R.B.. Determination of nitrogen structures on activated carbon surfaces by a chemical method. Fuel, 76(5). 381-384 (1997). 

Fig. 10 Left-hand side-. A typical amorphous structure, quenched to 200 GPa. The bonds that cross the periodic boundaries are not shown. Right-hand side Passivated amorphous nitrogen structure. The hydrogen atoms are shown in dark gray and the nitrogen in light gray...

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