Polyhalogenated alkane

Cytochrome P450 reduction of polyhalogenated alkanes has been demonstrated. For example, cells of Pseudomonas putida G786 containing cytochrome genes on the CAM plasmid were... 

Substructures commonly found in dyes (chromophores), fluorescent compounds, pesticides (polyhalogenated alkanes, cycloalkanes). 

Carbon-carbon bond formation is a fundamental reaction in organic synthesis [1, 2,3,4], One way to form such a bond and, thus, extend a carbon chain is by the addition of a polyhalogenated alkane to an alkene to form a 1 1 adduct, as shown in Scheme 1. This reaction was first reported in the 1940s and today is known as the Kharasch addition or atom transfer radical addition (ATRA) [5,6], Historically, Kharasch addition reactions were conducted in the presence of radical initiators or... 

Ekstrom, M. (1988). Electron transfer in reductions of polyhalogenated alkanes. Thesis, Lund University Evans, C. A. (1979). Aldrichim. Acta 12(2), 23... 

Electrochemical reduction of a variety of polyhalogenated alkanes has been undertaken. Stepwise dechlorination of gem-dichloro- and gem-trichloroalkanes occurs. Dichloromethane can be reduced in the presence of an olefin to form a cyclopropane [25], and... 

The values of the reaction rate, for polyhalogenated alkanes in Fe(II)/goe-thite suspensions are noted in Table 16.3 together with their pseudo-rate constants and half-lives. The reaction rates are affected by contact time, sorption density, and solution pH. Pecher et al. (2002) note that a contact time of 20 hours is necessary... 

Treatment of perhalogenated and highly halogenated alkenes with sulfur tetrafluoride in the presence of lead(IV) oxide, which is most likely converted in situ into lead(IV) fluoride, results in addition of fluorine to the C = C bond of the alkenes. The addition proceeds at 100 C to afford per- and polyhalogenated alkanes 5 in yields ranging from a few percent to almost quantitative.190 Representative examples are given. 

Nucleophilic Displacement of Halogens at Saturated Carbon Atoms Box 13.1 The Concept of Hard and Soft Lewis Acids and Bases (HSAB) Illustrative Example 13.2 Some More Reactions Involving Methyl Bromide Illustrative Example 13.3 1,2-Dibromoethane in the Hypolimnion of the Lower Mystic Lake, Massachusetts Polyhalogenated Alkanes — Elimination Mechanisms... 

In this, as in many other cases in aqueous solution, OH" plays the role of the base. Note that for compounds such as 1,1,2,2-tetrachloroethane and pentachloroethane, the base catalyzed reaction is important at quite low pH values (/NB = 4.5, i.e., pH at which the neutral and base catalyzed reaction are equally important, see Table 13.7 and Section 13.3). In fact, for polyhalogenated alkanes a small7NB value (e.g., <7) is indicative of an E2 reaction, or, in special cases, of an E1CB reaction see below. Some other examples of compounds reacting by an E2-mechanism include 1,1,2-trichloro-ethane, 1,1,2-tribromoethane, and l,2-dibromo-3-chloroethane (see Table 13.7). A high /NB value (e.g., >10) does not, however, necessarily exclude ( elimination, because this reaction may also occur with water as base, or by an alternative to the SN1 mechanism (i.e., an El mechanism, see below). 

Perlinger, J. A., R. Venkatapathy, and J. F. Harrison, Linear free energy relationships for polyhalogenated alkane transformation by electron-transfer mediators in model aqueous systems , J. Phys. Chem. A., 104,2752-2763 (2000). 

For polyhalogenated alkanes, the most general elimination reaction is the 1,2 elimination (Equation (8)). These reactions can be mediated by water, acid, or base. However, base-mediated reactions are studied most widely. 

Photolysis of allyltriorganogermanes in the presence of CCI Br and other polyhalogenated alkanes... 

Besides promoting the Kharasch addition reaction of polyhalogenated alkanes to MMA,the [RuCl2(PPh3)3] complex (1) also initiates the controlled polymerization of MMA, provided that the XCC13 concentration is kept low. Thus, the switch between the polymerization and the 1 1 Kharasch addition reaction depends solely on the relative concentration of the polyhaloalkane ( the initiator in polymerization reactions) to the metal catalyst. Using near-to-... 

The range of ruthenium alkylidene catalysts active in radical chemistry was further enlarged to the readily accessible vinylidene complexes 4 and 5 [33]. Catalyst precursors 4 and 5 were tested for the ATRA of polyhalogenated alkanes with various olefins. Substitution of one phosphine in 4 by an NHC improves its catalytic efficiency. This is a surprising result given that 3 is more ac-... 

Irrespective of the mechanistic pathway, radical anions from a acceptors undergo very rapid bond cleavage, a process that might be related to the toxicity [44] and carcinogenic activity [45] of polyhalogen alkanes, and which is of huge importance in synthetic chemistry. 

Pecher K., Haderlein S. B., and Schwarzenbach R. P. (1997) Transformation of polyhalogenated alkanes in suspensions of ferrous iron and iron oxides. In 213th ASC National Meeting, April 13-17, 1997. ASC Division of Environmental Chemistry, Washington, EX2, pp. 185-187. 

From polyhalogenated alkanes it is possible to prepare compounds containing more than one aromatic ring ... 

Similarly, the fluoromethanes have F—C bonds that shorten128 as the number of fluorines increases from one in 2.87 to four in 2.90, and the number of generalised anomeric effects accumulates. The bond-strengthening represented by these bond-shortenings contributes to the reduced reactivity towards nucleophilic substitution seen in polyhalogenated alkanes. 

Subsequent studies (28) have led to the development of one-step, high-yield syntheses of l,l -diiodo-, l,l -dibromo-, and l,l -dichloroferro-cene from reactions involving l,l -dilithioferrocene prepared with either the halogens, p-toluenesulfonyl halides, or polyhalogenated alkanes at... 

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