Polyhalogenated aromatic

TEF Values for Polyhalogenated Aromatic Hydrocarbons Used in a Study of Residues in Fish... 

Palladium NHC systems for the hydrodehalogenation of aryl chlorides and bromides and polyhalogenated aromatic substrates originate from about the same time as the first reports on Ni chemistry, and show many similarities. Initial efforts showed that the combination of PdCdba) (2 mol%), one equivalent of imidazolium chloride and KOMe produced an effective system for the reduction of 4-chlorotolu-ene, especially upon use of SIMes HCl 2 (96% yield of toluene after 1 h at 100°C) [7]. Interestingly, higher ligand to metal ratios severely inhibited the catalysis with only 7% yield of toluene achieved in the same time in the presence of two equivalents of SIMes HCl 2. Variation of the metal source (Pd(OAc)2, Pd(CjHjCN)jClj), alkoxide (NaOMe, KO Bu, NaOH/ ec-BuOH) or imidazolium salt (IMes HCl 1, IPr HCl 3, lAd HCl, ICy HCl) all failed to give a more active catalyst. 

A particular instance of iron overload being associated with liver injury, with free radicals again being implicated, is the hepatic porphyria and hepatocarcinoma induced by polyhalogenated aromatic chemicals. This is described separately below. 

Polyhalogenated Aromatic Chemicals, Iron and hepatic Porphyria... 

Murk, A.J., T.J. Boudewijn, P.L. Meininger, A.T.C. Bosveld, G. Rossaert, T. Ysebaert, P. Meire, and S. Dirksen. 1996. Effects of polyhalogenated aromatic hydrocarbons and related contaminants on common tern reproduction integration of biological, biochemical, and chemical data. Arch. Environ. Contam. Toxicol. 31 128-140. 

One example for the reaction of a 229-type copper reagent is shown in Equation (128). Neopentyl-substituted organocopper reagent 230, which bears aldehyde, is generated followed by treatment with acetyl chloride to provide coupling product 231 in 70% yield. Application of this method to the selective functionalization of polyhalogenated aromatics was also reported.497... 

Immune Modulation byTCDD and Related Polyhalogenated Aromatic Hydrocarbons... 

The influence of electron density distiibution in the radical-anioa on the rate of carbon-halogen bond cleavage was discussed on page 94. This effect makes possible the selective dehalogenation of polyhalogen aromatic compounds. Examples... 

Murk, A.J., Bosveld, A.T.C., Berg, M. van den and Brouwer, A. (1994a). Effects of polyhalogenated aromatic hydrocarbons (PHAHs) on biochemical parameters in chicks of the common tern (Sterna Hirundo). Aquat. Toxicol. 30(2), 91-115. 

Murk, A. J., Leonards, P.E.G., VanHattum, B., Luit, R., Van der Weiden, M., Smit, M.D. (1998). Application of biomarkers for exposure and effects of polyhalogenated aromatic hydrocarbons in naturally exposed European otters (Lutra lutra). Environ Toxicol Phar-macol 6 91—102. 

Brouwer A. 1998. Structure-dependent multiple interactions of polyhalogenated aromatic hydrocarbons with the thyroid hormone system. Organohalogen Compounds 37 225-232. 

Sanderson JT, Aarts JMMJG, Brouwer A, et al. 1996. Comparison of Ah receptor-mediated luciferase and ethoxyresorufm-O-deethylase induction in H4IIE cells Implications for their use as bioanalytical tools for the detection of polyhalogenated aromatic hydrocarbons. Toxicol Appl Pharmacol 137 316-325. 

Dioxins (PCDDs) and furans (PCDFs) are polyhalogenated aromatic hydrocarbons of high toxicity. There are a total of 210 different congeners 75 dioxin congeners and 135 furan congeners, of which 17 are potentially toxic. Dioxins and furans are now found prevalent in air, water, and soil in almost all natural environments. PCDD/Fs are strongly bound to organic matter, where half-life in soil has been estimated at 10-20 years (Ryan et al., 1987). PCDD/Fs enter the environment primarily as unintentional byproducts of combustion and chemical processes. 

Jackson, J.A., Diliberto, J.J., Bimbaum, L.S. (1993) Estimation of octanol-water partition coefficients and correlation with dermal absorption for several polyhalogenated aromatic hydrocarbons. Fundam. Appl. Toxicol. 21, 334-344. 

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