Priorities compound classes

Wilson and McNabb (1) have suggested that the population density of microbiota below the root zone in North American probably exceeds the bacterial biomass in the rivers and lakes on the continent. Biochemical measures of the biomass and metabolic actmty of subsurface biota indicate that the biomass is largely bacterial (8). Microbial biotransformation potential has been demonstrated in the laboratory for compounds in a number of priority pollutant classes (9-101... 

As one and the same compound can exhibit the characteristics of more than one compound class and may also be a combination of several parent substructures, seniorities must be laid down, i.e., rules allowing the assignment of priorities. 

This naming method is used only for a limited number of compound classes which are listed in Table 9 in descending order of priority. In contrast to substitutive nomenclature, parent systems are named here in the guise of their radicals , i. e. substituent groups, to which are added, separated by a space, the anionized names of the compound class in question. Some examples may illustrate the principles of this nomenclature type ... 

Chapters 1,2, and 3 of this book have dealt in some detail with the nomenclature rules for parent structures and the wealth of different functional compound classes based there upon. The present chapter will recapitulate once again in a more summary manner the most important directives for the construction of the complete names of more complex compounds. This entails a reconsideration of the question of priorities for ring and chain systems already briefly approached in the pertinent sections of Chapter 1. Since functional groups must ultimately be included in the decisions, extension of the priority rules becomes imperative, as will be shown in the following sections. 

The different functional categories of the selenazoles have been classed in according to the functional priority or to the quantity of prepared compounds. 

In order of decreasing priority for citation of a functional class name, and the prefix for substitutive nomenclature, are the following related compounds ... 

The different classes of compounds that have been successfully separated by MEKC include, among others, phenols [932,933], antioxidants [930,934], vitamins [935], phthalate esters [931,936] (Figure 4.26) and charged and neutral dyestuffs, including some dispersive dyes [937-939]. The separation of various priority... 

Five compounds classified as priority pollutants contain an ether moiety and halogen atoms attached to the aryl and alkyl groups. Five pesticides are suspected to contain at least one compound from this class. B/i(2-chloroethyl) ether (BCEE) is used as a raw material in two pesticides BCEE itself functions as a fungicide or bactericide in certain applications. In the other three pesticides, the ethers are suspected to be present as raw material impurities. 

Each class of the aforementioned organic pollutants may include hundreds of substituted compounds. For example, chlorinated benzenes may include one hexachlorobenzene, a pentachlorobenzene, three dichlorobenzenes, and three trichlorobenzenes. Table 2.1 lists 100 priority pollutants classified by the USEPA. 

Polycyclic aromatic hydrocarbons represent a class of compounds of great environmental concern due to their suspected mutagenic and carcinogenic properties [42-47]. Unease over the potential adverse health effects of polycyclic aromatic hydrocarbons is evident in the recent inclusion of P6 polyaromatic hydrocarbons in the Environmental Protection Agency s priority contaminates list. Polycyclic aromatic hydrocarbon contaminates pose several potential health risks due to the persistence of these compounds in the environment [48,49], their tendency to strongly bind to soil surfaces [50-52], and their presence in a wide variety of common media (air, dust, soil and food) [53]. Possible risks are associated with skin contact, inhalation or ingestion of contaminated dust, soil, or air, and ingestion of contaminated food. 

It sets out a priority-based ranking scheme for compounds according to level of health concern based on extent of human exposure and assessed or presumptive toxicological effects. In the absence of actual test data, presumptive toxicity also can be anticipated from chemical structure-activity relationships or from the nature of the substance and the known biological activity of substances of the same or similar structural class. This information can provide guidance on how much toxicology testing should be done for certain levels of human exposure. 

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