Halogen compounds, organic mechanisms

A key step in the reaction mechanism appears to be nucleophilic attack on the alkyl halide by the negatively charged copper atom but the details of the mechanism are not well understood Indeed there is probably more than one mechanism by which cuprates react with organic halogen compounds Vinyl halides and aryl halides are known to be very unreactive toward nucleophilic attack yet react with lithium dialkylcuprates... 

Many recent reports on the radiolysis of organic halogen compounds have involved studies of solid state or very low temperature systems (refs. 745, 781, 787, 858, 867, 906, and the use of pulsed techniques - - - - - - . Studies on species adsorbed on silica gel have also been made. The nature of intermediate species and the mechanism of scavenger action have been discussed by a number of investigators (see, for example, references 749, 906, 974, 981). 

Besides other occurrences of vanadium where the underlying biochemical mechanism is not understood (Rehder 1992, Mohammad et al. 2002a,b, Semiz et al. 2002, Semiz and McNeill 2002), vanadate-dependent non-heme oxidases are involved in the halogenation of organic compounds (see Section 1.2.1.7 Ohshiro etal. 2002, Sarmah et al. 2002, Tanaka et al. 2002, Ohsawa et al. 2001). Due to its high availability and its unique chemical features, more functions for vanadium as trace element may be uncovered in the future. 

The organization is fairly classical, with some exceptions. After an introductory chapter on bonding, isomerism, and an overview of the subject (Chapter 1), the next three chapters treat saturated, unsaturated, and aromatic hydrocarbons in sequence. The concept of reaction mechanism is presented early, and examples are included in virtually all subsequent chapters. Stereoisomerism is also introduced early, briefly in Chapters 2 and 3, and then given separate attention in a fuU chapter (Chapter 5). Halogenated compounds are used in Chapter 6 as a vehicle for introducing aliphatic substitution and elimination mechanisms and dynamic stereochemistry. 

Windawi, H. and Wyatt, M. (1993) Catalytic destruction of halogenated volatile organic compounds mechanisms of platinum catalyst systems. Platln. Met. Rev., 37,186-193. 

Windawi H, Wyatt M. Catalytic Destruction of Halogenated Volatile Organic Compounds Mechanisms of Platinum Catalyst Systems. Platinum Met Rev 1993 37 186-193. 

Nucleophilic substitution is one of a variety of mechanisms by which living systems detoxify halogenated organic compounds introduced into the environment Enzymes that catalyze these reactions are known as haloalkane dehalogenases The hydrolysis of 1 2 dichloroethane to 2 chloroethanol for example is a biological nude ophilic substitution catalyzed by a dehalogenase... 

Chemical Properties. A combination of excellent chemical and mechanical properties at elevated temperatures result in high performance service in the chemical processing industry. Teflon PEA resins have been exposed to a variety of organic and inorganic compounds commonly encountered in chemical service (26). They are not attacked by inorganic acids, bases, halogens, metal salt solutions, organic acids, and anhydrides. Aromatic and ahphatic hydrocarbons, alcohols, aldehydes, ketones, ethers, amines, esters, chlorinated compounds, and other polymer solvents have Httle effect. However, like other perfluorinated polymers,they react with alkah metals and elemental fluorine. 

Successful thermal decarboxylation of metal arenoates other than poly-halogenoarenoates are restricted to mercury compounds and fall into three categories, namely (i) those where electron-withdrawing substituents other than halogens are present in the organic groups, (ii) those where substituents and/or conditions are used which favor a different mechanism, e.g., classic electrophilic aromatic substitution, or (iii) those where the conditions are sufficiently forcing for both mercuration and decarboxylation to occur. 

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