Classification, Nomenclature, and Examples of Environmental Organic Chemicals

Classification, Nomenclature, and Examples of Environmental Organic Chemicals 

Let us start out by a few comments about the terms used to describe carbon skeletons encountered in organic molecules. When considering a hydrocarbon (i.e., a compound consisting of only C and H) or a hydrocarbon group (i.e., a hydrocarbon substituent) in a molecule, the only possible functionalities are carbon-carbon double and triple bonds. A carbon skeleton is said to be saturated if it has no double or triple bond, and unsaturated if there is at least one such bond present. Hence, in a hydrocarbon, the term saturated indicates that the carbon skeleton contains the maximum number of hydrogen atoms compatible with the requirement that carbon always forms four bonds and hydrogen one. A saturated carbon atom is one that is singly bound to four other separate atoms. 

With respect to unsaturated hydrocarbons we should note that compounds exhibiting one or several double bonds are often called alkenes or olefins. Finally, we need to add a brief note concerning the nomenclature in aromatic systems, particularly, in six-numbered rings such as benzene. Here the terms ortho-, meta-, and ara-substi-tution are often used to express the relative position of two substituents in a given ring system. Identically, we could refer to those isomers as 1,2-(ortho), 1,3-(meta), 1,4-(para) disubstituted compounds (see margin). 

Hydrocarbons are ubiquitously in the environment. Natural hydrocarbons range widely in size from methane to /3-carotene (Fig. 2.12) many other branched, ole-finic, cyclic, and aromatic hydrocarbons are found in fossil fuels, or tend to derive 

PAHs are also of great ecotoxicological concern. It is, therefore, not surprising that these compounds are among the most intensively investigated organic pollutants. Hence, they will serve us as important model compounds throughout this book. 

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