Alkali metal dechlorination

Alkali metal dechlorination processes are water sensitive. Soil moisture content can adversely affect the reaction in in-situ soil applications. The application of alkali metal dechlorination is generally expensive. 

Residuals Produced The residual produced from the alkali metal dechlorination of soils is reported to be an alkaline soil which requires neutralization. 

Tetrahalobenzynes, however, react with a variety of aromatic compounds to afford tetrahalobenzobarrelene derivatives in good yields, frequently in the range of 55 to 75%. The dehalogenation of a variety of alkenyl chlorides with alkali metals in tetrahydrofu-ran containing tert-butyl alcohol suggested this approach to the dechlorination of tetrachlorobenzobarrelenes. 

Pentachloropyridine undergoes a regio-selective dechlorination to give 2,3,5,6-tetrachloropyridine [118]. The reduction of 1- and 2-phenoxynaphthalene at the cathode or by an alkali metal afforded phenol and naphthalene. The intermediacy of the naphthalene radical has been made probable by the use of an internal radical trap [119]. 5-Aryloxy-l-phenyltetrazoles cleave reductively predominantly at the tetrazolyl-O bond. The relative rates of... 

Although the CFCs are not as stable as the fluorocarbons (FCs), they are unusually stable compounds. Dichlorodifluoromethane, CCI2F2 (CFC-12), is stable at 500°C in quartz. Trichloromonofluoromethane, CCI3F (CFC-11), begins to decompose at 450° C. The CFCs react with molten alkali metals and CCI2F2 reacts vigorously with molten aluminum, but with most metals they do not react below 200°C. An exception is the dechlorination of chlorofluorocarbons with two or more carbon atoms in the presence of Zn, Mg, or A1 in polar solvents. ... 

Over the last five years, U.S. ERA has supported research on a chemical dehalogenation process for destroying PCB and dioxin. Nucleophilic displacement of aromatic halides by alkali-metal polyglycoxides occurs readily at elevated temperatures. This reaction readily dechlorinates PCB in mineral oil at 100° and proceeds similarly with 1,2,3,4- TCDD in organic solvents. The addition of dipolar, aprotic solvents such as dimethyl sulfoxide increases the reaction rate and allows dechlorination reactions in dry systems at ambient conditions. Initial tests of this concept for soil decontamination at Shenandoah Stables, Missouri, failed because of high moisture content of the soil and low temperatures. The process was used successfully in the summer of 1986 to remove penta-, hexa-, hepta-, and octachlorodibenzodioxins from... 

Further dechlorination may occur with the formation of substituted diphenyhnethanes. If enough aluminum metal is present, the Friedel-Crafts reactions involved may generate considerable heat and smoke and substantial amounts of hydrogen chloride, which reacts with more aluminum metal, rapidly forming AlCl. The addition of an epoxide inhibits the initiation of this reaction by consuming HCl. Alkali, alkaline-earth, magnesium, and zinc metals also present a potential reactivity hazard with chlorinated solvents such as methylene chloride. 

Alkali or alkaline metals dissolve readily in liquid ammonia to give blue solutions of die metal cation and solvated electrons. Independendy,our group and Commodor Solution Technologies reasoned diat solvated electron solutions would rapidly dechlorinate chlorinated organics and this... 

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