Specific Families of Compounds

In addition to these general warnings you should be aware of the severe hazards posed by some more specific families of compounds. The compounds listed in Table 2.2 pose a severe risk of explosion and those in Table 2.3 should be regarded as extremely toxic. 

Empirical QSPR Correlations In quantitative structure property relationship (QSPR) methods, physical properties are correlated with molecular descriptors that characterize the molecular and electronic structure of the molecule. Large amounts of experimental data are used to statistically determine the most significant descriptors to be used in the correlation and their contributions. The resultant correlations are simple to apply if the descriptors are available. Descriptors must generally be generated by the user with computational chemistry software, although the DIPPR 801 database now contains a table of molecular descriptors for most of the compounds in it. QSPR methods are often very accurate for specific families of compounds for which the correlation was developed, but extrapolation problems are even more of an issue than with GC methods. 

There are variations of Equation 3.14 for specific families of compounds, i.e. using different relationships for the adjustable parameters I (which can be also related to the Hansen solubility parameters). On average I is equal to 0.8 for many homologous series of compounds, but it should be obtained... 

Chemical composition does not generally come into play, except for the case where it is necessary to establish maximum specifications for undesirable compounds such as sulfur, nitrogen, and metals, or even more unusually, certain compounds or families of compounds such as benzene in premium gasolines. By tradition, the refiner supposedly possesses numerous degrees of freedom to generate products for which the properties but not the composition are specified. 

However, this conventional method presents a certain number of limitations. In the first place, the traditional end-use property itself can be difficult to determine. Consider the cetane number for example is it a good characterization of diesel fuel with respect to its behavior in commercial diesel engines In the second place, concern for protecting the environment imposes new specifications which are often specifications linked to the composition of products very low content of certain contaminants, reduced levels of certain families of compounds, or even a specific compound as already discussed. 

Abstract The Ebro river basin is one of the most studied basins in Spain. The Confederation Hidrografica del Ebro (CHE), which is the organization in charge of the management of the basin, has different control networks that are operative since 1992. Besides these control networks, there is also a contribution of scientific studies since 1988 to know the distribution of persistent organic pollutants in the basin. Most of these studies are site specific or consider only one family of compounds. Recently, some scientific studies have focused on the basin as a whole, considering several compounds and matrices. 

Additionally, there are specialized studies designed to address endpoints of concern for almost all drugs (carcinogenicity, reproductive or developmental toxicity) or concerns specific to a compound or family of compounds (local irritation, neurotoxicity, or immunotoxicity, for example). When these are done, timing also requires careful consideration. It must always be kept in mind that the intention is to ensure the safety of people in whom the drug is to be evaluated (clinical trials) or used therapeutically. An understanding of special concerns for both populations should be considered essential. 

Condensate release might be equated to the release of volatile constituents but are often named as such because of the specific constituents of the condensate, often with some reference to the gas condensate that is produced by certain petroleum and natural gas wells. However, the condensate is often restricted to the benzene, toluene, ethylbenzene, and xylenes (BTEX) family of compounds. 

Despite the fact that the hydrolysis of the ferric ion is exceedingly sensitive to various experimental parameters (temperature, pH, etc.), hematite (a-Fe203) and akageneite ((3-FeOOH) were apparently the first reasonably uniform colloidal metal (hydrous) oxides dispersions reported in the literature, as already indicated in the introduction. Since then, this family of compounds has been the most extensively investigated, with specific emphases on particle uniformity, composition, and morphology. 

In this review, quantitative aspects of the structure and reactivity of these compounds are treated first. New developments in the fields of synthesis and reactivity are examined next. As a consequence of their relevance for the development of new materials23-27 and the possibilities they offer for analytical purposes, the number of studies in which thiocarbonyl compounds act as ligands of a variety of metal ions has increased in an almost explosive way. Recent reviews28-30 are also available on specific families of coordination compounds involving thiocarbonyl ligands. A concise survey of the present status of these studies is presented in the last section. 

Benzodiazepines are a family of compounds that share the same basic chemical structure and pharmacological effects. Although the more famous members of this family are associated with treating anxiety (e.g., diazepam [Valium] see later in this chapter), several benzodiazepines are indicated specifically to promote sleep (Table 6-1). These agents exert hypnotic effects similar to those of nonbenzodiazepines—such as the barbiturates—but benzodiazepines are generally regarded as safer because there is less of a chance for lethal overdose.22 Benzodiazepines, however, are not without their drawbacks, and they can cause resid-... 

Similar to opioids, the cannabinoid system appears to be intricately involved in normal physiology, specifically in the control of movement, formation of memories, and appetite control. Basic research has discovered that members of this family of compounds have the capacity to protect threatened neurons, thereby slowing neurodegenerative processes that ultimately lead to physical disability. As the function of the physiological role of endocannabinoids becomes clearer, it appears the system may be involved in the pathology of several neurological diseases, specifically multiple sclerosis, spasticity, and pain. In 1999 the German journal, Forschende Komplementar-medizin und Klassische Naturheilkunde (Research in Complementary and Classical Natural Medicine) commented ... 

Clays are a family of crystalline aluminosilicate solids that interact with a variety of organic compounds (Theng, 1974). Acid treatment develops acidic sites by removing aluminum from the structure and often enhances the reactivity of the clay with specific families of organic compounds. The acid sites also catalyze the formation of coke, and Houdry developed a moving bed process that continuously removed the coked beads from the reactor for regeneration by oxidation with air (McEvoy, 1996). 

Assignments of NMR resonances obtained from families of compounds at equilibrium to specific structure-building segments appear to be somewhat more complicated than in the previous case. But here also methods have been devised which permit an unequivocal assignment and which will be discussed in the following sections. 

The following is a partial listing of families of compounds that are known to have reactivity with water.1 Depending upon the specific compound, the reaction can be rapid and even violent, or simply slow hydrolysis. 

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