Halogens alkanes and

Nucleophilic Substitution Hydrolytic Reactions of Halogenated Alkanes and Alkanoates... 

Rosenkranz HS. 1977. Mutagenicity of halogenated alkanes and their derivatives. Environ Health Perspect 21 79-84. 

The production of nitromethane and its use as a solvent, fuel additive, stabilizer for halogenated alkanes, and intermediate may result in the release of nitromethane into the environment, principally into the atmosphere. Human exposure to nitromethane may additionally occur via dermal contact and accidental ingestion of methanol-nitromethane fuel mixtures (Kaiffer et al., 1972 Sandyk Gillman, 1984 Dayal et al., 1989 De Leacy et al., 1989 Lundberg, 1989 National Toxicology Program, 1997 Mullins Hammett-Stabler, 1998). 

A variety of halogenated alkanes and alkenes such as hexachlorobutadiene, chlorotrifluoro-ethylene, tetrafluoroethylene, and trichloroethylene (Fig. 7.28) are nephrotoxic. Studies have shown that metabolic activation is necessary for toxicity, but this does not involve cytochromes P-450. Thus, hexachlorobutadiene (HCBD) is a potent nephrotoxin in a variety of mammalian species, and the kidney is the major target. 

Nirmalakhandan and Speece [36] introduced the polarizability factor,, as an additional molecular descriptor. They derived the following model for halogenated alkanes and alkenes, alkylbenzenes, halobenzenes, and alkanols ... 

Van der Waals Parameter-Kow Relationships Moriguchi et al. [40] have studied the correlation of Kow with either the van der Waals volume, Vvaw, or the van der Waals surface area, Aw, for apolar organic compounds such as inert gases, alkylbenzenes, PAHs, and halogenated alkanes and benzenes. The relationships are... 

The first term, representing acid-"catalyzed" hydrolysis, is important in reactions of carboxylic acid esters but is relatively unimportant in loss of phosphate triesters and is totally absent for the halogenated alkanes and alkenes. Alkaline hydrolysis, the mechanism indicated by the third term in Equation (2), dominates degradation of pentachloroethane and 1,1,2,2-tetrachloroethane, even at pH 7. Carbon tetrachloride, TCA, 2,2-dichloropropane, and other "gem" haloalkanes hydrolyze only by the neutral mechanism (Fells and Molewyn-Hughes, 1958 Molewyn-Hughes, 1953). Monohaloalkanes show alkaline hydrolysis only in basic solutions as concentrated as 0.01-1.0 molar OH- (Mabey and Mill, 1978). In fact, the terms in Equation(2) can be even more complex both elimination and substitution pathways can operate, leading to different products, and a true unimolecular process can result from initial bond breaking in the reactant molecule. 

Chlorpyrifos can be fit to a QSAR Wolfe (1980) developed. The calculated as well as observed half-life of about 80 days falls in the middle of the set of diethyl-aryl-phospho-rothioates. The reactivity span of these compounds is much lower than that observed for the halogenated alkanes and alkenes, with half-lives generally within the range of several days to several years. 

Fishbein L. 1985. A survey of the analysis of halogenated alkanes and alkenes in biological samples. Chap. 7. In Fishbein L, O Neill IK, eds. Environmental carcinogens selected methods of analysis. Vol. 7-Some volatile halogentated hydrocarbons. Publication No. 68, International Agency for Research on Cancer (IARC), Lyon France, 141-168. 

Bromine will also halogenate alkanes, and it does so much more selectively than chlorine. For example, the following reaction yields text-butyl bromide with less than 1% of the primary isomer. 

PVP is a nonionic water-soluble polymer that interacts with water-soluble dyes to form water-soluble complexes with less fabric substantivity than the free dye. Additionally, PVP inhibits soil redeposition and is particularly effective with synthetic fibers and synthetic cotton blends. The polymer comprises hydrophilic, dipolar imido groups in conjunction with hydrophobic, apolar methylene and methine groups. The combination of dipolar and amphiphilic character make PVP soluble in water and organic solvents such as alcohols and partially halogenated alkanes, and will complex a variety of polarizable and acidic compounds. PVP is particularly effective with blue dyes and not as effective with acid red dyes. 

Degradation of Halogenated Alkanes and Alkenes 6.4.1 Elimination Reactions... 

A variety of halogenated alkanes and alkenes such as hexachlorobutadiene, chlorotrifluoroethylene,... 

Alkynylsilanes—reactive precursors and versatile synthons for various reactions—can be obtained mainly by silylation techniques of metallated alkynes (including Grignard derivatives), or by elimination reactions of halogenated alkanes and alkenes in the presence of a silylating agent. The main classes of alkynylsilanes will be discussed as well as some derivatives which may be of further interest to organic synthesis. 

The disappearance rate constants for a large number of halogenated hydrocarbons, which include halogenated alkanes and alkenes, in anoxic sediment-water systems were correlated with several molecular descriptors (Peijnenburg et al.,... 

Equation 3.51) and experimentally determined rate constants (k p) for the series of halogenated alkanes and alkenes. 

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. 

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