Hexachlorocyclohexane isomers

That benzene hexachloride isomer mixture is then the raw material for lindane production. The production of lindane per se is not a chemical synthesis operation but a physical separation process. It is possible to influence the gamma isomer content of benzene hexachloride to an extent during the synthesis process. Basically, however, one is faced with the problem of separating a 99%-plus purity gamma isomer from a crude product containing perhaps 12 to 15% of the gamma isomer. The separation and concentration process is done by a carefully controlled solvent extraction and crystallization process. One such process is described by R.D. Donaldson et al. Another description of hexachlorocyclohexane isomer separation is given by R.H. Kimball. 

Rosa R, Rodriguez-Farre E, Sanfeliu C. 1996. Cytotoxicity of hexachlorocyclohexane isomers and cyclodienes in primary cultures of cerebellar granule cells. J Pharmacol Exp Ther 278(1) 163-169. 

N-Heterocyclics la 252 lb 268 Hexachlorocyclohexane lb 227 Hexachlorocyclohexane isomers lb 211 Hexacyanoferrate(II) anions lb 307 Hexacyanoferrate(ni) anions lb 307 n-Hexadecanol esters, alkaline hydrolysis la 63... 

Rodrlguez-Garrido B, MC Arbestain, MC Monterroso, F Macfas (2004) Reductive dechlorination of a, 3,5, and y-hexachlorocyclohexane isomers by hydroxocobalamin in the presence of either dithiothreitol or titanium(III) citrate as reducing agents. Environ Sci Technol 38 5046-5052. 

Although quite extensive use of has been made in studies on the degradation of alkyl sulfonates (Hales et al. 1986), C1 has achieved only limited application on account of technical difficulties resulting from the low specific activities and the synthetic inaccessibility of appropriately labeled substrates. One of the few examples of its application to the degradation of xenobiotics is provided by a study of the anaerobic dechlorination of hexachlorocyclohexane isomers (Jagnow et al. 1977), the results of which are discussed in Chapter 7, Part 3. 

Suar M, JR van der Meer, K Lawlor, C Holliger, R Lai (2004) Dynamics of multiple lin gene expression in Sphingomonas paucimobilis B90A in response to different hexachlorocyclohexane isomers. Appl Environ Microbiol 70 6650-6656. 

Short chained chlorinated paraffins (SCCP) Hexachlorocyclohexane isomers (HCH)... 

Polychlorinated dibenzodioxins (PCDDs) Polychlorinated dibenzofurans (PCDFs) Polychlorinated biphenyls (PCBs) Polyaromatic hydrocarbons (PAHs) Pentachlorophenol Short chain chlorinated paraffins Hexachlorocyclohexane isomers Mercury and organic mercury compounds Cadmium... 

Paschke, A. and Schuurmann, G. Concentration dependence on the octanol/water partition coefficients of the hexachlorocyclohexane isomers at 25 °C, Chem. Eng. Technol, 23(8) 666-670,1998. 

Fischer RC, Kramer W, Ballschmiter K (1991) Hexachlorocyclohexane isomers as markers in the water flow of the Atlantic Ocean. Chemosphere 23(7) 889-900... 

The most fundamental properties of a chemical substance are those of the substance in pure form, in most cases as a solid or liquid. Molecular mass can be deduced readily from the chemical formula or structure, although a range of values may exist for commercial mixtures. In some cases, the substance may adopt different structural (e.g., cis-trans) or enantiomeric forms, usually with relatively small physical property differences but with potentially substantial differences in ability to induce toxicity or other biological responses. The hexachlorocyclohexane isomers and enantiomers are examples, the insecticide lindane or y HCH being the most active form. 

Willett, K.L., Ulrich, E.M., Hites, R.A., 1998. Differential toxicity and environmental fates of hexachlorocyclohexane isomers. Environ. Sci. Techol. 32, 2197-2207. 

DDTs), hexachlorocyclohexane isomers (HCHs), chlordane compounds (CHLs) and hexachlorobenzene. Residues levels of industry-derived contaminants such as polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-/>-dioxins and dibenzofurans (PCDD/Fs) were also reviewed. Concentrations of these contaminants in different environmental compartments were expressed as unit equivalent to part-per-billion (ppb) level, unless otherwise specified. The cited values of concentrations from various literature sources were rounded to two significant digits for comparison. A number of factors can influence the concentrations in biological samples. Therefore, whenever possible, for biological samples the lipid normalized concentrations were cited for comparison. 

Formyl-hydrazino)-4-(5-nitro-2-furyl) thiazole Furan Gyromitrin Flexachlorobenzene Flexachloroethane Flexamethyl phosphoramide Hydrazine Hydrazine sulfate Hydrazobenzene Indeno [1,2,3-cd] pyrene Isoprene Lead (II) acetate Lead chromate Lead phosphate Lindane (and other hexachlorocyclohexane isomers)... 

Hiihnerfuss, H. Faller, J. Kdnig, W.A. Ludwig, R, Gas chromatographic separation of the enantiomers of marine pollutants. 4. Fate of hexachlorocyclohexane isomers in the Baltic and North Sea Environ. Sci. Technol. 1992, 26, 2127-2133. 

Law, S.A. Diamond, M.L. Helm, P.A. Jantunen, L.M. Alaee, M., Factors affecting the occurrence and enantiomeric degradation of hexachlorocyclohexane isomers in northern and temperate aquatic systems Environ. Toxicol Chem. 2001, 20, 2690-2698. 

Padma, T.V. Dickhut, R.M., Spatial and temporal variation in hexachlorocyclohexane isomers in a temperate estuary Mar. Poll. Bull. 2002, 44, 1345-1353. 

Buser, H.-R. Miiller, M.D., Isomer and enantioselective degradation of hexachlorocyclohexane isomers in sewage sludge under anaerobic conditions Environ. Sci. Technol 1995,29,664-672. 

Zander AK, Chen JS, and Semmens MJ, Removal of hexachlorocyclohexane isomers from water by membrane extraction into oil. Water Research 1992, 26(2), 129-137. 

Comparing microwave-assisted extraction (MAE) with ASE is as complicated as comparing the latter with SFE. In fact, the comparison cannot rely exclusively on recoveries as these are usually similar [30,62,73,114,116], so it must be made in other terms. For example, while ASE performs better than MAE and SFE in the extraction of hexa-conazole from aged contaminated soils — the more aged the soil, the better — [68], MAE is to be preferred to ASE for the extraction of hexachlorocyclohexane isomers from soils when expeditiousness is crucial (ASE allows up to 12 samples to be processed simultaneously, which results in substantially decreased total analysis times) [73]. 

Tanabe S, Tanaka H, Tatsukawa R. 1984. Polychlorobiphenyls, DDT and hexachlorocyclohexane isomers in the western North Pacific ecosystem. Arch Environ Contam Toxicol 13 731-738. 

Figure 4. Inhibition by hexachlorocyclohexane isomers of specific 2 nM [35S]TBPS binding to rat brain membranes.

In addition to the hexachlorocyclohexane isomers, technical BHC also contains hepta- and octachlorocyclohexane isomers as a result of the additive chlorination of monochlorobenzene and dichlorobenzenes, formed as by-products in the reaction. 

The herbicides of this group are mostly superseded and replaced by less toxic chemicals. Pentachlorophenol (PCP, 1) was introduced in 1936 as a timber preservative in the United States. It is produced by catalytic chlorination of phenol (Stoesser, 1937). Other procedure for the synthesis of pentachlorophenol uses the inactive hexachlorocyclohexane isomers as starting material. The isomer mixture is partially hydrolised, then from the polychlorophenol mixture formed pentachlorophenol is obtained by chlorination ... 

---