Compounds polyhalogenated aliphatic

Because of their useful properties, many polyhalogenated compounds are produced commercially. As industrial chemicals, they are usually given common names. 

Because some of these chlorinated compounds are suspected carcinogens, adequate ventilation is essential when they are used as solvents. 

Tetrafluoroethylene is the raw material for Teflon, a polymer related to polyethylene (Sec. 3.16) but with all of the hydrogens replaced by fluorine atoms. 

Nonpolymeric perfluorochemicals (hydrocarbons, ethers, or amines in which all of the hydrogens are replaced by fluorine atoms) also have fascinating and useful properties. For example, perfluorochemicals such as perfluorotributylamine, (CF3CF2CF2CF2)3N, can dissolve as much as 60% oxygen by volume. By contrast, whole blood dissolves only about 20%, and blood plasma about 0.3%. Because of this property, these perfluorochemicals are important components of artificial blood. 

Other polyhalogenated compounds that contain two or three different halogens per molecule are commercially important. The best known are the chlorofluorocarbons (CFCs, formerly known as Freons). The two that have been produced on the largest scale are CFC-11 and CFG-12, made by fluorination of carbon tetrachloride. 

---

The HDH products usually depended on electrolysis conditions, e.g. the electrochemical HDH of polyhalogenated aliphatic compounds produced various products at different potentials ... 

The purpose of this chapter is to give an overview of the chemical and biological processes that control the reactivity of Fe(II) in heterogeneous aqueous systems with respect to pollutant transformation. To this end, we will evaluate data collected in various laboratory systems as well as field studies. Two classes of model compounds with complementary properties will be used to monitor the reactivity of Fe(II) species in the various systems. Nitroaromatic compounds (NACs) primarily served to characterize the systems in terms of mass and electron balances. Reduction of NACs by Fe(II) species results in only a few major products (aromatic amines and hydroxy-lamines) which can be easily quantified by standard HPLC-UV methods in the low liM range. Polyhalogenated aliphatic compounds (PHAs) were used if little perturbation of the systems in terms of electron transfer to the organic substrates was crucial. Reduction of PHAs requires fewer electrons than nitro reduction and PHAs can be quantified by standard GC-ECD methods in the low ppb range. 

The elimination of solvents that interact specifically (hydrogen-bond donors, polyhalogenated and aromatic materials) seems necessary. It then appears that for the group of select solvents (l.e., polar, monofunctional aprotic, aliphatic compounds) left, all the scales correlate with each other to a good approximation (Table 15a). This has the led present authors to define a scale of polarity tt (32a) such that tt = (ir ), where (7t )c is the value of tt for a select solvent. (Cf. Table 15b). 

Rate constants for the reaction of hydroxyl radicals with different compounds were determined by Haag and Yao (1992) and Chramosta et al. (1993). In the study of Haag and Yao (1992) all hydroxyl radical rate constants were determined using competition kinetics. The measured rate constants demonstrate that OH0 is a relatively nonselective radical towards C-H bonds, but is least reactive with aliphatic polyhalogenated compounds. Olefins and aromatics react with nearly diffusion-controlled rates. Table 4-3 gives some examples comparing direct (kD) and indirect (kR) reaction rate constants of important micropollutants in drinking water. 

Aliphatic polyhalogenated compounds are sweet (chloroform, 1,2-dichloroethane, dichloromethane)... 

Molecular ion Fragments m/z 69 [M-501+- or [Frag-50]+ For saturated aliphatic halogen compounds often weak, for polyhalogenated compounds often absent Characteristic isotope patterns for Cl and Br CF3 CF2 ... 

In retrospect, the development and standardization of S-9 has centered around a limited number of chemical types, i.e., iV-nitrosamines, aromatic amines, and polycyclics. Accordingly, the ability of microbial systems supplemented with S-9 to detect these chemicals has been rather consistent. However, the converse also appears true chemicals, other than those types with which the testing has been standardized, that are metabolized in vivo to their active forms are not as consistently detected in such in vitro testing. While further discussion of this point is reserved for later, suffice it here to note that, in general, poorly activated types include azonaphthol dyes carbamyl and thiocarbamyl compounds phenyls polyhalogenated aromatics, cyclics, and aliphatics benzodioxoles and symmetrical hydrazines. 

Most alkyl halides and aromatic side-chain halides aliphatic -halogenated aldehydes, ketones, esters and acids. Polyhalogen compounds with more than two halogen atoms on one carbon atom (slowly) ... 

Often weak for saturated aliphatic halogen compounds, often absent from spectra of aliphatic polyhalogenated compounds... 

---