Method for halogens

Haglund P (1991) Isolation and determination methods for halogenated polycyclic aromatic compounds. Swedish EPA Rep 3905, p 145... 

The nature of bonding of the adsorbed species to the model cluster of metal surfaces can be analyzed in terms of the so-called constrained space orbital variation (CSOV) method. For halogen anions adsorbed on various silver surfaces, it has been found that Pauli repulsion, metal polarization, and charge transfer to the metal surface mainly contribute to the binding energy of the ions [104, 301]. 

In addition to the THM methods, EMSL-Cincinnati has developed purge and trap methods for selected halogenated (29) and aromatic (30) compounds that are considered to be chemical indicators of industrial contamination. The methods are applicable to 47 halogenated compounds (Method 502) and 33 compounds that have ionization potentials less than 10.2 eV and that are aromatic or contain a doubly bonded carbon (Method 503). Seven of these compounds are halogenated and are also included in the method for halogenated compounds. Another method, Method 524 (31), provides for GC-MS determination of 28 purgeable volatiles. Single laboratory precision and accuracy data for these compounds are provided in the EMSL methods. 

Reichert, J.K. and J. Lochtman. 1983. Testing methods for halogenated organic compounds. Experiences with drinking and surface waters. Environ. Technol. Lett. 4 15-26. 

Direct synthesis of sulfur based ionic liquids has been developed as a useful synthetic method for halogen free ionic liquids. The synthesis of sulfur based ionic liquids can generally be split in to two sections (1) sulphonate and (2) sulphate based ionic liquids (Scheme 9). The sulphate based salts are more common than the sulphonates. 

Interest in the use of reducing agents to activate C-F bonds was revived when systems that enabled selective removal of fluoride from perfluorocarbons were discovered in contrast to the complete (destructive) removal of halides as in sodium fusion reactions employed in methods for halogen analysis [31]. (Interest in this latter area has also had resurgence in the search for methods capable of destroying chlorofluorocarbons [32].) The key breakthrough was the report by MacNicol and Robertson that hexakis(thiophenoxy)napthalene can be prepared by treatment of perfluorodecalin with excess sodium phenylthiolate for 10 days at 70°C in DMF [33]. 

Catalytic Dehydrohalogenation A Chemical Destruction Method for Halogenated Organics... 

All analysis methods for halogenated VOCs found in literamre, are based on gas chromatography (GC) in combination with different detectors. In Table 17.1 a selection of GC analysis procedures for halogenated VOCs are tabulated. 

A more convenient method for halogenation of allylic and benzylic C-H moieties uses the readily available A-bromosuccinimide (NBS, 170) or NCS (173) with heat and/or light, in what is called the Wohl-Ziegler reaction. Reaction of NBS with cyclohexene in refluxing carbon tetrachloride gives bromocyclo-... 

Thermally enhanced hydrolysis is generally the most cost-effective remediation method for halogenated alkanes, and many funaigants and pesticides. A listing of common compounds with their hydrolysis half-lives at 100 °C is shown in Table 24.4. In situ thermal methods have been successfully used to hydrolyze 1,1,1-trichloroethane (TCA), 1,1,2,2-tetrachloroethane (TeCA), dichloromethane (methylene chloride), and ethylene dibronaide to remediate groundwater. 

Another method for halogen atom position change on a thiophene [25] was demonstrated for 2,5-dichlorothiophene. Under acidic conditions, this was converted into the isomeric 2,4-dichlorothiophene. Formation of a 2,5-dichloro-2/7-thiophenium ion then successive 1,2-migrations of chlorine and a proton lead to... 

Selective positional reduction is also possible as in the formation of 4-bromophenol from 2,4-dibromophenol and triphenylphosphine [59] and of 1, 4-dibromobenzene from 1, 2, 4-tribromobenzene and KOBu in dimethylsulphoxide [60]. Illustrative of recent methods for halogen displacement is the reduction of chlorobenzene with magnesium in isopropanol [61] and the photochemical reduction of p-chlorophenol to phenol (also in isopropanol) [62]. 

Kubaf T, Bodrog Z, Gaus M, Kohler C, Aradi B, Frauenheim T, Elstner M (2013) Parametrization of the SCC-DFTB method for halogens. J Chem Theory Comp 9(7) 2939-2949. doi 10.1021/ct4001922... 

H.A. Stefani, C.M.P. Pereira, R.B. Almeida, R.C. Braga, K.P Guzen, R. Celia, A mild and efficient method for halogenation of 3,5-dimethylpyrazoles by ultrasound irradiation using N-halosuccinimides, Tetrahedron Lett. 46 (2005) 6833-6837. 

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