Hydrocarbon derivatives containing nitrogen

Chapter 21 introduces aromatic hydrocarbons and their unique chemistry. In another class of aromatic compounds, heteroatoms replace one or more of the ring carbons. These compounds are collectively known as heterocycles or heterocyclic aromatic compounds, and they comprise a class of compounds so large that an entire course is easily built around their chemistry. Heterocycles are seen in several places in this book, including a brief introduction to their nomenclature in Chapter 5 (Section 5.6) and in Chapter 8 (Section 8.9). The most common heterocycles include five- and six-membered monocyclic derivatives that contain nitrogen, oxygen, or sulfur. Several important bicyclic derivatives contain nitrogen. The use of heterocycles in medicine and industry is extensive. This chapter will expand the aromatic chemistry from Chapter 21 and introduce the world of heterocyclic chemistry. 

Essential oils may comprise volatile compounds of terpenoid or non-terpe-noid origin. All of them are hydrocarbons and their oxygenated derivatives. Some may also contain nitrogen or sulphur derivatives. They may exist in the form of alcohols, acids, esters, epoxides, aldehydes, ketones, amines, sulphides, etc. Monoterpenes, sesquiterpenes and even diterpenes constitute the composition of many essential oils. In addition, phenylpropanoids, fatty acids and their esters, or their decomposition products are also encountered as volatiles [1-16, 21-33, 36-38]. 

Creosote. The major portion of creosote is derived from coal and is a complex mixture of aromatic hydrocarbons with condensed ring systems. The remaining components are tar acids, which are phenolic derivatives of these compounds, and tar bases, which are heterocyclic compounds containing nitrogen plus some neutral oxygenated compounds. At least 200 chemical compounds have been identified in coal-tar creosote, but many of these are present in small amounts. The chemical composition is variable, but some idea of a typical creosote is given in Table I (2). 

Petroleum chemicals are synthetic organic chemicals including hydrocarbons and derivatives containing oxygen, nitrogen, sulfur, the halogens, synthesized from fractions of crude petroleum or natural gas hydrocarbon components (70). 

Mass spectral analysis of the municipal refuse-derived oil ( ) identified only two long chain fatty acids with certainty however, not more than traces of aromatics were determined to be present. The manure-derived oil was found to be largely alicyclic hydrocarbon but contained heterocyclic nitrogen and alkyl phenollcs ( ). These claims of the saturated hydrocarbon nature of the oil products are at odds with the reported elemental analyses (see Table I). The low hydrogen to carbon ratios dictate that the oil products must contain a large fraction of aromatic or, at least, highly unsaturated compounds. 

For hydrocarbons and their various derivatives containing oxygen and nitrogen atoms, a long history of thermochemical investigation has left a legacy of experimental standard enthalpy of formation values (approximately 3000 have been compiled by Pedley et al. [25]). 

Hydrocarbon derivatives are compounds that can be synthesized from a hydrocarbon. These derivatives contain not only carbon and hydrogen, but such additional elements as oxygen, nitrogen, or a halogen. The compounds in each class have similarities in structure and properties. We will consider the classes of hydrocarbon derivatives shown in Table 19.4, which is divided into two sections of different color. The compounds in the first section don t contain a C O group in their molecules, while those in the second section all contain a C O group. A carbon atom double bonded to an oxygen atom is called a carbonyl g roup. 

This review article contains "best" values of bond-dissociation energies at 298.15 K of hydrocarbons and their nitrogen, oxygen, sulfur, halogen, and silicon derivatives. There is also some limited data on inorganic molecules. 

Essential oils may consist of volatile constituents of terpenoid or nonterpenoid origin. These compounds are hydrocarbons and their oxygenated derivatives. Some also may contain nitrogen or sulfur derivatives. They may exist in the form of alcohols, acids. 

Nitro-PAHs are polycyclic aromatic hydrocarbon derivatives that contain one or more nitro groups covalently bound at chemically reactive positions on the aromatic ring. Mixtures of nitrated PAHs are generated either by reactions of PAHs with nitrogen oxides or as byproducts of the incomplete combustion of fossil fuels (65). A wide variety of nitro-PAHs have been isolated from environmental sources, such as coal fly ash, diesel emission particulates, cigarette smoke and carbon black photocopier toners (29, 52, 63, 74, 75, 86, 87, 88). Structures of representative nitro-PAHs isolated from the environment are shown in Figure 1. 

Coal tar is the condensation product obtained by cooling to approximately ambient temperature, the gas evolved in the destmctive distillation of coal. It is a black viscous Hquid denser than water and composed primarily of a complex mixture of condensed ring aromatic hydrocarbons. It may contain phenoHc compounds, aromatic nitrogen bases and their alkyl derivatives, and paraffinic and olefinic hydrocarbons. Coal-tar pitch is the residue from the distillation of coal tar. It is a black soHd having a softening point of 30—180°C (86—359°F). 

Allyl (27, 60, 119-125) and benzyl (26, 27, 60, 121, 125-133) radicals have been studied intensively. Other theoretical studies have concerned pentadienyl (60,124), triphenylmethyl-type radicals (27), odd polyenes and odd a,w-diphenylpolyenes (60), radicals of the benzyl and phenalenyl types (60), cyclohexadienyl and a-hydronaphthyl (134), radical ions of nonalternant hydrocarbons (11, 135), radical anions derived from nitroso- and nitrobenzene, benzonitrile, and four polycyanobenzenes (10), anilino and phenoxyl radicals (130), tetramethyl-p-phenylenediamine radical cation (56), tetracyanoquinodi-methane radical anion (62), perfluoro-2,l,3-benzoselenadiazole radical anion (136), 0-protonated neutral aromatic ketyl radicals (137), benzene cation (138), benzene anion (139-141), paracyclophane radical anion (141), sulfur-containing conjugated radicals (142), nitrogen-containing violenes (143), and p-semi-quinones (17, 144, 145). Some representative results are presented in Figure 12. 

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