Aromatic structures nitrogen-containing

The organic chemical structural types believed to be characteristic of coals include complex polycyclic aromatic ring systems with connecting bridges and varied oxygen-, sulfur-, and nitrogen-containing functionalities. 

Two nitrogen containing heterocyclic aromatic compounds—pyrimidine and purine— are the parents of the bases that constitute a key structural unit of nucleic acids... 

Two nitrogen-containing polymeric materials with extended aromatic ladder structures have been chosen for direct fluorination studies (Figure 14.9).57 Pyrolyzed polyacrylonitrile (3) and paracyanogen (4) [poly(pyrazinopryazine)] have been subjected to direct fluorination to produce perfluorinated analogues. 

The pyridine nucleotides NAD and NADP always function in unbound form. The oxidized forms contain an aromatic nicotinamide ring in which the positive charge is delocalized. The right-hand example of the two resonance structures shown contains an electron-poor, positively charged C atom at the para position to nitrogen. If a hydride ion is added at this point (see above), the reduced forms NADH or NADPH arise. No radical intermediate steps occur. Because a proton is released at the same time, the reduced pyridine nucleotide coenzymes are correctly expressed as NAD(P)H+HT... 

Naphthenic acids and sulfur- and nitrogen-containing heterocycles and naphthenic-aromatic compounds can all be found at various concentrations in distillate fuel fractions. Degradation through condensation-type reactions rather than through radical initiated polymerization is typically more common in distillate fuel. Because of this, degradation products are often quite complex in nature and structurally diverse. 

TABLE 10.3 Structures, Common Names, Empirical Formulas, and Molecular Weights of Selected Nitrogen-Containing Mono- and Polycyclic Aromatic Compounds (N-PACs) Identified in Ambient Air... 

Table III shows elemental composition of typical sour petroleum, coal syncrudes or shale oils. Compared with typical sour petroleum, the coal syncrude is lower in sulfur content but significantly higher in nitrogen. Compared with shale oil, coal syncrude is lower boiling and contains only about one half the nitrogen. A major difference between the two liquids is the highly aromatic structure of coal liquids and the absence of long paraffinic structures. Shale oil is more aromatic than petroleum but significantly less aromatic than coal liquids. This is mirrored by the hydrogen contents which were shown in Table I.

Schultz, T.W., Moulton, B.A. (1985) Structure-activity relationships for nitrogen-containing aromatic molecules. Environ. Toxicol. Chem. 4, 353-359. 

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