Hydrocarbon derivatives containing oxygen

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). 

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]). 

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]. 

Coal tars are by-products of the carbonization of coal to produce coke and/or natural gas. Physically, they are usually viscous liquids or semi-solids that are black or dark brown with a naphthalene-like odor. The coal tars are complex combinations of polycyclic aromatic hydrocarbons, phenols, heterocyclic oxygen, sulfur, and nitrogen compounds. By comparison, coal tar creosotes are distillation products of coal tar. They have an oily liquid consistency and range in color from yellowish-dark green to brown. The coal tar creosotes consist of aromatic hydrocarbons, anthracene, naphthalene, and phenanthrene derivatives. At least 75% of the coal tar creosote mixture is polycyclic aromatic hydrocarbons (PAHs). Unlike the coal tars and coal tar creosotes, coal tar pitch is a residue produced during the distillation of coal tar. The pitch is a shiny, dark brown to black residue which contains polycyclic aromatic hydrocarbons and their methyl and polymethyl derivatives, as well as heteronuclear compounds... 

Carotenoids are tetraterpenes derived from a symmetrical C40 skeleton. Carotenoids can be classified into two great groups carotenes, which are strictly hydrocarbons, and xanthophylls, derived from the former that contain oxygenated functions. Stracturally, the carotenoids may be acyclic (e.g., lycopene) or contain a ring of five or six carbons at one or both ends of the molecule (e.g., /3-carotene). Figure 10.1 shows the stmcture and the system of numbering using lycopene and /3-carotene as models of acyclic and bicyclic carotenoids respectively. Stractures of some representative carotenes and xanthophylls, commonly found in fruits are also illustrated. 

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