Halogens, reduction potentials chlorine

The electron affinities of halogenated aromatic and aliphatic compounds and nitro compounds have been evaluated. Additional electron affinities for halogenated benzene, freons, heterocyclic compounds, dibenzofuran, and the chloro- and fluoroben-zenes are reported from ECD data. The first positive Ea for the fluorochloroethanes were obtained from published ECD data. The Ea of halogenated aromatic radicals have been estimated from NIMS data. The AEa of all the halobenzenes have been calculated using CURES-EC. The Ea of chlorinated biphenyls and chlorinated napthalenes obtained from reduction potentials have been revised based on variable solution energy differences. 

The effectiveness of the purification by the halogens depends on their oxidation-reduction potentials and decreases from chlorine to iodine. In addition, the latter can disproportionate ... 

Chemical oxidizers used to disinfect RO systems include hydrogen peroxide (peroxide), halogens, and ozone. Although halogens (and specifically chlorine) are the most popular oxidizers using in conjunction with RO pretreatment, they do not have the highest oxidization-reduction potential (ORP). Table 8.8 lists the ORP for several oxidizers. As the table shows, ozone and peroxide have nearly twice the ORP or oxidative power as chlorine. Despite the relatively low ORP, chlorine is the most commonly used disinfectant in brackish water RO pretreatment due to its ease of use and its ability to provide residual disinfection (for seawater desalination using RO, bromine (as HOBr)... 

The trends in the standard reduction potentials of the halogens are closely related to the uniqueness of fluorine. A quick inspection of Table 18.1 indicates that fluorine has the highest standard reduction potential (2.87 V) of the group and that chlorine is a distant second (1.36 V), with the rest of the values steadily decreasing from 1.07 V to 0.3 V after that. Note that the standard reduction potentials correspond to the half-reaction shown in Equation (18.6) ... 

Reductions Microbial and mammalian nitroreductase reduces nitro compounds to amines. Chlorinated alkanes and alkenes are common contaminants in ground water and chlorinated aromatics, PCBs, organochlorine pesticides, are often detected in soils and sediments and it has been of interest to evaluate the potential for these compounds to be metabolized. A number of microorganisms are able to dechlorinate both halogenated aliphatic and aromatic compounds in a reduction reaction." It has been observed that the more highly chlorinated congeners are more reactive in these systems in contrast to the response in oxidative dechlorinations. 

A further, somewhat more efficient route to the propellane is the electrochemical reduction of the dibromide (195 X = Br) at relatively negative electrode potentials. Formation of the tricyclic hydrocarbon was again demonstrated by its trapping with halogen, the addition of chlorine giving a 12 % yield of (195 X = Cl) after 5 h reduction at -2.35... 

Studies in the last decade show that iron sulfide minerals are very reactive in the reductive transformation of chlorinated aliphatic pollutants. These minerals, present in sulfate-reducing anaerobic environments, likely contribute to in-sUu transformation of chlorinated aliphatic pollutants and have potential application in remediation technologies. Solution pH, the presence of organic co-solutes with functional groups representative of natural organic matter, and the thermodynamic or molecular properties of the halogenated aliphatic pollutant all influence the rates and/or products of pollutant transformation. 

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